How to Increase the Energy Efficiency of Your Existing Home

I am an energy auditor and weatherization contractor working primarily in the residential market in Central Pennsylvania. Through a variety of tests, I can tell a homeowner not only what home improvements should be done to improve the efficiency of the home, but also what the return on investment will be. Apart from the energy savings, I also pay particular attention to the health and safety of the home.

Energy auditing and building analysis is a fairly new industry. I received my training in Maine, through Maine Housing, and at the Weatherization Training Center at Penn College. I also went through the Building Performance Institute's Building Analyst certification.

I would like to share some of the tricks of my trade with the community. I will also share an average of the return on investments that I have seen on my jobs. As I go through a home, these are the items I typically look at:

  • The building shell (air sealing)
  • Insulation
  • Combustion analysis (furnace or boiler analysis)
  • Ducts
  • Water heater
  • Lighting
  • Base load appliances
  • Water conservation
  • Health and safety
  • Phantom loads
  • Solar
  • Windows and doors
The Building Shell (Air Sealing)

All homes have an air barrier, but some are, of course, better than others. An air barrier basically helps to reduce the amount of conditioned air that is lost and replaced by unconditioned air. The faster a building exchanges air with the outside, the more energy is needed to maintain the structure at a comfortable temperature. There are always holes in your air barrier, because otherwise you would suffocate in your home. The trick is to keep the number of holes to an acceptable level without compromising safe and healthy ventilation.

I use a blower door, which is essentially a door frame, tarp, and fan that goes in an exterior door, hooked up to a pressure manometer. Basically, this test gives me the CFM leakage of the structure at 50 pascals of pressure. While the fan is running, I can typically find leaks using various techniques and equipment. Based on the structure, the leakage number, and the subsequent tests, I then determine if it is safe to seal up the house further, where to seal, and what potential savings are to be gained.

I would not recommend performing air sealing on a house without having a blower door test done by a BPI certified Building Analyst. For example, maybe your house is right on the border of allowing mold to develop. You proceed to seal the house too tight, and mold begins to develop in the bathrooms or kitchen. Perhaps you have many pets and odors that are tolerable with your leaky house when they are quickly exchanging with the fresh outdoor air, but then you seal the house up to a point where the smells become unbearable. Or you might encounter the biggest fear of any building analyst, the possibility of a backdrafting flue causing carbon monoxide poisoning.

In my experience, older homes tend to be leakier than new homes. Air sealing in the attic is typically the best place to start. Recessed lights, plumbing chases, wire intrusions, open wall cavities, and attic hatches are common leakage points. If you are sealing a recessed light, make sure you follow local fire code.

If you would like to learn more about specific air sealing techniques, the Department of Energy link below has some good information at this site.

ROI on Air Sealing – AVG 18%
(It really varies on the structure, energy prices, how difficult the air sealing techniques are, and how good your contractor is at finding and sealing the biggest leaks. The materials are usually inexpensive, but can use a lot of labor)

Your thermal barrier, or insulation, will determine the ability of your home to retard heat flow. The slower your heat leaves your home, the less energy your heating system will use. Your air barrier and thermal barrier should be together and continuous for maximum efficiency. It is very important that you air seal before installing new or additional insulation. Insulation is another job I would recommend hiring a BPI certified building analyst before tackling.

The typical insulation install in an existing home is installed in the attic. Sidewalls and rim joists can also be done in certain homes. It is important to do the proper attic prep before adding any insulation. This may include the following:

  • Determine amount (In PA, code is R-38: about 11 inches of blown cellulose or fiberglass.)
  • Check electrical (Watch out for knob and tube wiring, or any frayed wires or overburdened junctions.)
  • Make insulated boxes to go over any non-IC-rated recessed lights
  • Metal flashing with fire-safe caulk to keep insulation away from chimney or flue
  • Air sealing all intrusions into attic (If air sealing is not done, condensation can occur in attic, leading to mold, derated insulation, and ice dams.)
  • Ventilation (Make sure soffit vents have proper vents to train air flow to ridge vent and also make sure blocking is installed to prevent new insulation from clogging vents. Installing insulation without proper vents and blocking can lead to wind washing that will derate your insulation.)
  • Dams may need to be installed to prevent insulation from spilling over attic hatches, air handlers, and vents
  • Any roof leaks must be addressed
  • Watch out for vermiculite, as it has been known to contain asbestos, which can cause cancer. It should be removed by an asbestos-removal contractor.

(photo: vermiculite)

Blowing sidewalls and floors can be a very difficult job, and the only houses that typically make sense to do this in are those without insulation that have large wall cavities and balloon framing. This is definitely a job for the professionals.

Rim joist insulation can be an effective install for those homes with uninsulated rim joists. Below is a nice video that shows where the rim joist is. A homeowner or even a contractor can simply use rigid board insulation, friction fit and foamed on the edges with cans of spray foam, for sufficient improvement. The more expensive spray foam with the large canisters in the video is not necessary.

I personally prefer to use loose blown cellulose insulation. It is essentially recycled newspaper. I prefer this to fiberglass as it is non-toxic, resists air, and will seal small air leaks, where fiberglass will not stop air and is quickly derated when windwashing is present. I do use fiberglass on occasion, and it is certainly an effective form of insulation. Closed-cell foam insulation is the "new kid on the block." It is a perfect air barrier with a high R value, but it is expensive. It is a good to use if you are insulating a roof deck where you are bringing the entire attic inside the thermal envelope; for example, when you have ducts and an air handler in the attic.

(photo: Cellulose Insulation)

ROI on insulation: AVG. 17%
(Varies depending on difficulty of the install, and how much insulation there is. The less existing insulation there is, the higher the ROI.)
Combustion Analysis (Furnace or Boiler analysis)

I do a combustion analysis on Oil and Gas systems to determine efficiency, draft, CO, O2, among other things. Typically the 80% + systems and below will progressively lose efficiency after they have been tuned. It is a good idea to have your system professionally maintained. It really does make a big difference.

Oil boilers and furnaces: The best systems are typically 85% efficient. If you have an older system, it could be around 60% or 70% efficiency. If you have an older system, I would highly recommend discussing replacement with your HVAC professional. If no natural gas is available and you have the funds, switching to a geothermal heat pump is a great way to go. It is on the pricey side, as I have seen systems for 30K, but paybacks can approach 10%, depending on how much oil you are using.

Gas Furnaces or Boilers: Natural gas is so cheap right now, and the high efficiency 95% + units are affordable and extremely efficient. This is a nice option if you have a natural gas line that you can tap into. If you have an older 70%+ unit, a high efficiency replacement unit can give you a 10-15% payback, and with the sealed combustion, CO is no longer a major concern.

Electric Resistance Heat: This is by far the most expensive way to heat a house. It is a great idea to switch to natural gas if you have access to a gas line, or to geothermal if you have the funds. High-efficiency natural gas units can yield a 20% ROI, while a geothermal heat pump can yield a 10% ROI.

Size really does matter: One problem in almost every home that I audit is that the heating system is oversized. Does your system frequently turn on and off? Or does it run constantly? A perfectly sized system will run constantly on a cold day. A perfectly sized system will not be able to heat your house to 72 degrees on the coldest day of the year. Combustion heating systems run at their maximum efficiency at steady state. When a system starts and stops, it runs at a much lower efficiency than the unit’s rated efficiency. Fantastic savings can be gained by air sealing and insulating, thereby reducing the heating load on a home, and then the heating system can be replaced with a smaller, more efficient system.

(photo: 90% + condensing furnace)

ROI on heating system replacements: 7%-25%
(Varies dependent on how inefficient the current system is, what fuel source, rebates, and cost.)
ROI on tune up for combustion equipment: 50%
(Possibly more depending on how out-of-tune your equipment is.)
Duct Sealing and Insulation

If your ducts are entirely inside the thermal envelope, or conditioned area, this is typically not a problem. You can seal ducts in this situation to help balance your furnace. This becomes critical when you have ducts in a crawl space or attic. Any leaks in the ducts will help to heat that attic or crawl space. This can, of course, waste energy, but it can also lead to condensation issues, as the conditioned warm air hits the cool roof deck or crawl space. A very easy fix for sealing your ducts is to use duct mastic to seal up all the joints and connections. Mastic is good because it does not come off like tape and can expand and contract. It is a paste that can be spread with a brush or just an old glove that you are willing to sacrifice.

Ducts in unconditioned spaces should be insulated to R-11. It is possible to lose 10-30% of a home’s heating and cooling energy through the conduction of uninsulated ducts.

ROI on duct sealing: AVG 14%
(Varies on fuel type, prices, accessibility, but also offers many residual benefits to the HVAC.)
ROI on duct insulation: AVG 22%
(Varies on fuel, prices, job difficulty.)
Water Heaters

The first thing to look at is the temperature. 120 degrees usually works well. Make sure your water is not hotter than that. You can check the water heater, as some do have settings, but you may have to put a thermometer under hot water to find out. Constantly keeping a tank at too high a temperature is extremely expensive.

The second thing to be concerned about are the water pipes. Are they insulated? If not, insulate starting from the tank, 6’ on the cold side, and as much of the warm side as you can reach. This will help you reduce standby loss, and it is super easy and cheap also. In some situations water heater tank wrap can also be installed, but be careful because in some water heaters, a wrap will void the warranty. Make sure to check the manual to find out if a wrap is appropriate. Most new water heaters are already insulated.

Should you consider replacement? If you have an electric water heater, I would strongly recommend the new air source heat pump water heaters. They use less than half the electricity of a traditional electric water heater. Solar hot water is another nice option, especially those that are concerned about steady supplies of traditional energy in the future. On-demand tankless systems work well if you use natural gas for your water heating, especially if you are moving from an inefficient tank model (non-condensing unit, atmospherically vented). However, with natural gas so cheap, the ROI is not great, and if you have a heavy hot-water need, you may need more than one.

(photo: Air Source Heat Pump Water Heater)

ROI pipe insulation- AVG 27%
(Big ROI because improvement is so cheap)
ROI new air source heat pump water heater- AVG 23%
ROI Solar hot water- 7%-15%
(Varies based on fuel, can be higher with rebates)
ROI tankless Gas- 4%-7%
(Varies based on type replacing, fuel prices)

Incandescent, CFL’s, or LED’s are the predominant lighting choices available to most homeowners.





Dims well; cheap; most people like the quality of the light

Not efficient; emits waste heat. Does not last long.

Compact Fluorescent

Affordable; uses 20% of the electricity of an incandescent

Mercury inside if broken. Some people do not like the quality of the light.  


Extremely long-lasting; uses 1/3 the electricity of a CFL

Very expensive; some people feel the light is too dim.


ROI CFL’s- AVG 96%
(Depending on how many hours per day the light is used)
ROI LED’s- AVG 16%
(Depending on how many hours per day the light is used)

There are only a couple of appliances that I am concerned about considering replacing, as far as efficiency goes. The number one appliance is the fridge/freezer. The second would be the washing machine, and a distant third and fourth would be the dishwasher and the non-energy-star dehumidifier. Here is a link to a nice database for refrigerators and freezers to give you an idea of how many KWH of electricity your current unit is using. Compare that to a new unit’s yellow energy sticker to determine the savings you would receive by replacement. Then, based on the cost and potential energy savings, you can easily decide if replacing your appliance is a good investment. Stay away from side-by-side fridges with built in icemakers, as they are more expensive and less efficient than typical top-freezer models.

Front-load washing machines use a lot less water, water heat, and electricity than top-load washers. Whenever replacing a top load, pick an energy star front load. Dishwashers should only be replaced for an energy-star model if you have a pre-1994 model. Otherwise, use it until it breaks. Non-energy-star dehumidifiers are a good item to replace, but it would be even better to remove the source of the moisture so that you do not need the dehumidifier whenever possible.

Fridge Replacement: AVG 21%
Washer Replacement: AVG 11%
Dishwasher Replacement: AVG 8%
Dehumidifier Replacement: AVG 9%
Water Conservation

Low-flow showerheads, faucet aerators, and low-flow toilets are a great way to save water, along with whatever fuel you are using to heat your water, as well as your sewer bill. Most showerheads will tell you on the head how many GPM they allow to flow. Low-flow showerheads typically allow 1.5 GPM. If you have a showerhead with 2.0 GPM of flow or higher, it is a good idea to replace it with a low-flow showerhead. Bear in mind that you will have less pressure and water with a low-flow head, although the new designs do a good job of aerating the water. Low-flow faucet aerators are also 1.5 GPM. It is a good idea to replace the aerators that are 2.0 GPM or higher. The aerators are super cheap, and you will not sacrifice anything to achieve the water savings.

Low-flush toilets typically use 1.6 gallons per flush, although I have seen lower, while older toilets can use 3.5 GPF. There are also dual-flush toilets that allow even lower GPF for liquid waste. Switching to a low-flow toilet can save 20,000 gallons of water per year. Composting toilets are a good solution for those off the grid, or who want to remain independent of the public sewer.  


(photo: Aerated water)                 

ROI low flow showerhead: AVG. 50%
(Varies, dependent on fuel source, water prices, GPM of former head, and water use)
ROI Faucet Aerators 1.5GPM: AVG. 70%
(Varies, dependent on fuel source, water prices, GPM of former head, and water use)
ROI low flow toilet 1.6 GPL: AVG. 28%
(Varies, dependent on water prices, former GPF amount, and sewer)
Health and Safety

CO and moisture/mold are the two biggest things that I am concerned about, as far as health and safety, when I am looking at a house. I can always tell who has a wet basement when I drive by a house and see relatively new paint peeling off. This is from the vapor pressure of the moisture. Excess moisture will literally take years off the life of your home. Below is a list that I give my clients to help them to keep their house safe, healthy, and durable.

Living in a healthy home and avoiding mold and mildew:

  1. Avoid unvented space heaters
  2. Don't overcool the house in the summer
  3. Don't hang drying clothes inside
  4. Don't dry wood indoors (no storing firewood inside)
  5. Use kitchen and bath fans at least 3x the duration of shower or cooking
  6. Enhance room circulation with fans to avoid cold spots
  7. Avoid storing items against cold outside walls or in damp basements
  8. Avoid storing vulnerable materials in damp basements
  9. Run a humidistat equipped dehumidifier during summer in damp basements
  10. Additional pets and people add moisture; be aware of increased ventilation needs if adding occupants.
  11. New construction adds tremendous moisture to home for the first years as materials are drying
  12. Make sure dryer is always vented outside
  13. Never store the following inside: paints, solvents, grease, oil, pesticides, gas equipment, kerosene space heaters
  14. Don’t warm your car up in the garage, if garage is attached to the house. 
  15. Beware of too many house plants, as they can add a lot of moisture to the home
  16. Make sure drain pipes are functional and sent away from the foundation (also keep gutters clean)
  17. Have heating equipment professionally maintained

(photo: mold in a bathroom)

Phantom Loads

Many appliances will draw electricity while plugged in but not in use. The trick is to find out which ones are drawing enough power to be concerned about either unplugging them or putting them on a power strip that you turn off. I use a handy tool called a watt meter to determine this. You can buy one for about $40. You plug the appliance into the watt meter and the meter into the outlet. Then read the results after it has had enough time to make a good yearly projection. Older televisions tend to be the biggest offenders that I find. People also tend to have these old TVs plugged into areas where they never use them, like the exercise area in the basement that they use twice a year. I have seen old TV’s that can use 400 KWH just sitting there plugged in for a year.

Items that tend to use a lot of power at rest

Items that do not use much at rest

TV’s, especially older ones


DVR’s, cable boxes

Phone Chargers

Older Computers

Printer (must be turned off)

Old Fashioned Jukebox


TV/ VCR combos

Playstation 2




ROI phantom load removal: 200% AVG
(Does require some occupant discipline to turn off power strips when not in use)
Solar Power Photovoltaic

I did sell some solar systems prior to the PA Sunshine rebates running out, and the ROI factoring in the 30% federal tax credit, the sunshine rebate, and the AEC’s (alternative energy credits) were excellent. I was getting about a 16% ROI on solar systems at this time. Now, with the PA Sunshine rebates no longer available, and the AEC’s dropping like a stone in recent months, the ROI has come down considerably. Having said that, I still think it is a viable investment, especially if you take into consideration the added resiliency. Below is an example of the current ROI on a 10 KW system without a battery backup:

(photo: 10 KW Sunpower roof mounted)

  • $7.00 per watt
  • cost = $70,000
  • Federal Tax Credit= $21,000
  • Adjusted Price= $49,000
  • PA power production: Appx. 12 MW per year (Provided full sun site, good pitch, and direction)
  • Electricity saved= $1800 per year at .15 per KWH
  • AEC’s: $1704 per year at current depressed rates
  • Savings: $3504 per year
ROI: 7.19%
Doors and windows

I have never sold a new window job, because the ROI is always terrible. The window industry certainly has some great advertising, because more often than not I have clients who think they need new windows. If you have old wood-frame single-pane windows, you are better off caulking, weatherstripping, and adding storm windows. If you already have double-pane or better windows, then simply caulking and weatherstripping, if needed, are sufficient. Doors are in a similar situation; just weatherstrip and make sure the door sweep is in good condition. The only time I would replace a door is when an interior door is used as an exterior door, but even then the ROI is not great. This is sometimes true if you have a door to the attic or to the garage. I have done the ROI calculations for window jobs for those past clients who would not take my word for it. See below:

ROI new windows: 3% AVG

Many utilities across the country and the federal government are offering rebates for energy-efficient measures and appliances. In PA, in accordance with Act 129, the utilities are offering big rebates for whole-house energy audits from participating contractors, as well as rebates for energy saving retrofits. As electricity, fuel oil, and natural gas get more expensive in a world of decreasing natural resources, the detailed improvements listed above will increase their effective ROI. I can’t imagine investing in anything until I took advantage of the great investment opportunities in my own home and infrastructure. As a bonus, you don’t have to worry about Goldman front-running you or the Fed printing too much insulation!

Phil Williams

BPI Certified Building Analyst, Energy Auditor


This What Should I Do? blog series is intended to surface knowledge and perspective useful to preparing for a future defined by Peak Oil.  The content is written by readers and is based in their own experiences in putting into practice many of the ideas exchanged on this site.  If there are topics you'd like to see featured here, or if you have interest in contributing a post in a relevant area of your expertise, please indicate so in our What Should I Do? series feedback forum.

If you have not yet seen the other articles in this series, you can find them here:

This is just an amazing post.
I know we’ve had many, many good ones, and this one just fits right in with the best of them.

Way to go Phil, nicely laid out and organized with plenty of supporting facts.

My oil tank is in my cellar.  This article mentions not storing oil inside your home.Is it possible in a colder climate to have the oil tank outside of the house?  I seem to remember hearing something about buried oil tanks no longer being allowed.
It also seemed to imply that old paint cans and other such things should not be kept in the house.  I currently keep these in the cellar and was planning to move them to the (under house) garage, which is basically part of the cellar.  Should I be moving these out to my shed?  What about them freezing in the winter?

Great Post Phil
I have a question about CFLs.  They are always advertised as lasting a long time, but I’ve had a problem with many of the bulbs going out after a few weeks or months of use.  Can you recommend the most reliable brand?  What is your experience with the LED lights? You mentioned that LEDs light have a long life span, but have you heard that they can fail early as well?

Another question.  Do you have any experience with solar air heaters such as the Solar Sheet or Cansolair and their effectiveness?

thanks a bunch


For the air source heat pump for water heating, the effeciency depends on where you live.

Overall, thank you for the post, it is helfpul.  I also recommend looking at reviews on Amazon, for what people experience for some of these, such as low flow faucets, etc.



Thanks for a wonderful post, it was really very informative and thoroughly enjoyable. It has sparked a few questions that maybe you could answer.

I recently signed with a contractor to install a solar hot water heater which is scheduled for installation in two weeks. Part of the proposed system is an electric hot water heater even though we currently use propane. The reason is that California offers a rebate of $1,200 +/- on electric hot water systems. By installing a $400 electric water heater, I get a $1,200 rebate. Crazy. Would an Air Source Heat Pump Water Heater be a better choice to work in conjunction with a solar hot water system?

Do you have any thoughts to share on radiant barrier retrofit for the attic? 

Does the ROI info that you’ve cited have a regional variation? I live in Southern California where the temps rarely ever get below freezing. Wouldn’t that affect the ROI?

Also, what is “wind washing” in regards to insulation?

Thanks again for a very valuable and timely contribution.

Phil thank you for a great review esp with ROI.  What is your opinion on retrofitting of energy recovery ventilation, and the various types and reliabilities (heat + latent/humidity)?



Phil - what a great post! All that excellent information in one place. I love the ROI calcs as well - very useful for giving people a context for prioritizing their energy efficiency efforts.
I had one question/point - you suggest that spray foaming the rim joist isn’t necessary and you prefer using rigid foam board fitted in and sealed. Isn’t that really time consuming? I’ve found that it can be a hassle to do that because joist spacing is variable in older homes and there are a lot of obstructions that require cutting and fitting. Whereas with spray foam, you don’t have to worry - you just spray it and in an hour, you’re done. And the spray foam gets in all nooks and crannies that I often see people miss when trying other methods.

I’ve put together an energy efficiency blog at  where I’ve been doing a brain dump on these types of issues and problems seen during my time doing energy audits. Hopefully, more of us will help spread the word and help empower people to make intelligent choices in retrofitting their homes.

Keep up the great work!


There is no end to how much securing the main living areas for comfortable living. And most people wouldn’t think the flushing has any efficent options till its too late. . . or until they are thirsty!
I’m sure this group has a long list of tips to add to the home front energy efficincy and here’s mine:

  • The project we're working on this summer at is to create a "double envelope" of mass around our buildings. The insulated mass (made of block, insulation and filled with sand) uses a single solar panel to collect heat from the attic - so it aids in cooling the house summers). This mass releases heat over winter. It can't heat our Minnesota home all winter but it can add early winter comfort.
  • The other winter heating we do with wood and all that has been discussed before on another topic. The only thing to add is to be sure to get an effcient burn on whatever wood you burn to save you time and increase your comfort. We may end up heating our mass system to get ALL the heat from our wood.
  • We actually do the same "mass storage system" but backwards for our ice house (we store the winter cold in anti-freeze/water tanks) and it is our freezer/cold house. The 12' x 12' insulated room is mainly tanks and was built in a building too far away for house use so I hope we can get a smaller - short cold storage built out the north door of the house (the north side stays cold here till June).
  • And not to forget landscapes become more energy efficient so looking at turning yards into gardens for food drops the fuel price but don't forget areas for kids and pets to run so look at the no mowing grasses to take over your high energy and time consuming lawns.
People will soon be finding many ways to become more efficent and it will be really interesting to see how uncomfortable people come up with new ways to conserve what little energy is available!

Thanks Again Phil!


[quote=cmartenson]This is just an amazing post.
I know we’ve had many, many good ones, and this one just fits right in with the best of them.
Way to go Phil, nicely laid out and organized with plenty of supporting facts.
It was my pleasure. I have benefited greatly from you and everyone else in the CM community. I am very happy that I was able to contribute something back.

[quote=joesxm2011]My oil tank is in my cellar.  This article mentions not storing oil inside your home.
Is it possible in a colder climate to have the oil tank outside of the house?  I seem to remember hearing something about buried oil tanks no longer being allowed.
It also seemed to imply that old paint cans and other such things should not be kept in the house.  I currently keep these in the cellar and was planning to move them to the (under house) garage, which is basically part of the cellar.  Should I be moving these out to my shed?  What about them freezing in the winter?
Old paint cans are typically OK in the garage, provided there is not a major connection between the garage and the house. For example, if you were to open a few cans in the garage, and then be able to smell them in the house, they should probably go to the shed, or better yet seal off the connections, but otherwise the garage is fine. Unfortunately, the paint can freeze, which can damage the paint, so depending on where you are located (how cold it is where you are) you may have to decide what is more important, your paint, or the possibility of breathing the paint fumes. The basement can be OK if the paint cans are new (not rusty) sealed very well. Having said that I personally do not like them in my house. I keep my paint and gas cans in my garage, which is unheated, but it is not directly connected to my house as their is an unconditioned breezeway separating the two. The oil tanks for heating systems can be in the basement, and they are outside as well. I would not worry about moving it, it should not be a problem. I was more referring to your gas cans, and oil cans for your outdoor power equipment.

Having CFL’s burn out early is a fairly common occurence. I do work for a couple of the PA utilities, and they force us to use a good grand of CFL, and I sometimes have these burn out immediately. Usually, I try a different wattage in this situation. A lot of times this works. Having said that GE makes a nice CFL, but they are expensive. I would not worry too much about the brand, and try changing the wattage. Also, sometimes it can be the electrical or the fixture. For example, I have a 4 pin CFL fixtures in my downstairs area, and a couple of those fixtures burn out quickly, but the rest of them have yet to be changed in three years. Below is the link for the company that I buy a lot of my bulbs from.
With the LED’s, I would not worry too much about them burning out quickly, as any worthwhile LED vendor will give you a 2 year warranty. Just check their warranty policy before you buy, because they are expensive. Also, I would highly recommend buying one from the store to determine if you like the light or not. I always show my clients samples first, and you would be surprised how many people say they hate the light. I personally really like LED’s, but they still do not have the variety available to always do a complete retrofit. Also, some of the higher wattages have fans in them, and they will make a buzzing sound that might drive you insane, if you like total quiet.
I like the idea of the solar air heater, but I do not have any personal experience with them. My opinion would be that it could save you some energy, but I would be careful relying entirely on the unit for heat, especially if you are in a harsh winter area.

I’m with Chris, this is one of the better posts.
I just had an energy audit done on my own home. After running the blower door and sealing some leaks, the auditors  were able to knock another 10% off the airflow, and this was after I had my exterior walls spray foamed, I sealed and caulked windows, doors, etc. I can imagine what the number was before I did all this. I’m now in the average CFM range for a home, but still just a bit higher than wher I should be. I don’t have the information from the audit in front of me, but I believe you want the CFM number to be in line with your home’s square footage. All in all, the audit was well worth it!

One thing that I have to somewhat disagree with is you mentioned running the bathroom exhaust fan after taking a shower. The humidity in my house was as low as 8% this past winter. To me, adding some humidity to the house via the shower is helpful. I read this in a green blog somewhere and it makes sense. 

What are your thoughts on adding insulation over existing insulation? I have some old rock wool insulation(only 2-3 inches thick) underneath my attic 2x6" deck floor. My original intent was to spray foam my attic rafters, but now I’m thinking of pulling up the floor and adding some fiberglass insulation directly on top of the existing rock wool. I’ve gotten mixed messages on doing this vs. ripping out all of the insulation and adding all new insulation.

Removing the paint cans from your house makes complete sense. Will do that tonight.

The phantom load was a big saving for me. I used that Kill-A-Watt meter and discovered my fridge was using twice as much power in a year as my dad’s fridge. I replaced the fridge with a new EnergyStar model.

Thanks again for an outstanding post.


Thanks for a wonderful post, it was really very informative and thoroughly enjoyable. It has sparked a few questions that maybe you could answer.
I recently signed with a contractor to install a solar hot water heater which is scheduled for installation in two weeks. Part of the proposed system is an electric hot water heater even though we currently use propane. The reason is that California offers a rebate of $1,200 +/- on electric hot water systems. By installing a $400 electric water heater, I get a $1,200 rebate. Crazy. Would an Air Source Heat Pump Water Heater be a better choice to work in conjunction with a solar hot water system?
Do you have any thoughts to share on radiant barrier retrofit for the attic? 
Does the ROI info that you’ve cited have a regional variation? I live in Southern California where the temps rarely ever get below freezing. Wouldn’t that affect the ROI?
Also, what is “wind washing” in regards to insulation?
Thanks again for a very valuable and timely contribution.
Thank you. The solar hot water system uses the electric heater for backup heat when needed and it houses the coils to heat up the tank from the solar. You are making a fantastic investment. In theory the air source electric water heater would certainly be more efficient than the traditional electric water heater, but the ROI would probably be much lower than stated in my article, because that ROI is based on an inefficient setup to start, just the traditional electric water heater. So it would only make a difference during the backup heat times, and in California, I would imagine that wouldn’t be too often. It is probably worth a call to your contractor to ask. My sense is that it would not be a great payback, but I do not know that through any hard numbers.  
Adding a radiant barrier to the underside of your roof can limit your heat gain in the summer. I would imagine this would be a nice retrofit in California, but here in PA with a short cooling season, I have never done one of these jobs. Having said that, one of the best ways to keep an attic cool, even more so than ventilation, is the color of your roof. Anyone out there looking to replace their roof, go with a very light color. Not only will it save on cooling, but the roof will last longer. I have a very light grey standing seam metal roof. Philadelphia had a white roof painting program a couple of years ago.
I’m glad you brought up the ROI based on region. It is absolutely tied to your climate. The ROI’s I stated above are just an average of jobs I have done here in Central PA. I could not speak with authority to the ROI’s you can expect in California. Having said that, certain formulas that I use do have weather data that can be changed. Homes that are more north of Harrisburg, PA can expect higher ROI’s on the insulation and air sealing work I detailed, but further south should expect lower. Those homes in primarily cooling climates are setup completely different, so you should consult a local BPI building analyst if you are in the South. The other items that are not tied to weather can certainly be a good guide for anyone, but bear in mind that every home is different. You may do better or worse with the ROI’s. You would do much better with solar in CA then what I see here in PA.
Windwashing is when outside wind comes in and pushes the heat out of your insulation faster than it would normally. For example, a home with soffit vents in the attic where the wind blows directly into the insulation. This will essentially speed up the time it takes for the heat to leave your thermal barrier. Remember your R-rating on your insulation is simply a function of how long it takes for the heat to pass through. If it passes through quicker it is effectively a lower R-rating than what you paid for.

Great article Phil… thank you!

I have 3 large 4’ x5’ lake view windows double glass old style not e-glass and
other smaller windows…

I am considering making “Interior Window insulation Panels” as done by
the Midcoast Green Colaborative:  (At Guy Marsden site… great resource also…).

I have seen these windows and the view is remarkably clear.

These are double sided with polyolefin shrink film and are cheap to make  $1.25/sq ft
or buy at $3/sq ft.  

You give new windows an ROI of 3%…
I think these inserts would have a Higher ROI… 
Great for leaky single pane windows less so for double pane like I have…

How would I calculate the ROI on this?    

Hot Water Heater

I currently have a HWH… conventional 30gal electric… AND I would think
that the recommended Air source Heat Pump hot water heater would make
my home cooler… which means during the heating months I would burn
more wood and propane to indirectly heat the water…  That in addition
to the complexity of the heat pump might affect my ROI… 

Air Conditioning

Normally here in Maine we don’t use an air conditioner because we live on lake
in largely shaded area… We do use “Maine Air Conditioning”  Open windows
at night, use a fan to cool house… Close window in the morning.

Probably a high ROI on this method! :slight_smile:

Health and Safety

Even though you recommend against it, we do dry some cloths and wet winter stuff
on a portable rack by the wood stove…   We also have an accurate greenhouse type
humidity indicator that averages around 40% relative humidity in the winter… even
with drying wet stuff near the wood stove.   We even crack open the bathroom to let
hot steamy air into the rest of the house during the winter… (Yes vent to outside in summer).

I believe that having some humidity in the house is healthy… along with a bedroom
at ~ 63 F in the winter… 

It is true on some very humid summer days the indoor humidity can reach 80% RH

Do you have guidelines for healthy temps and relative humidity?

Again, Thanks!

Bob O

         ERV’s and HRV’s are ventilation systems that I would use only in a supertight house that needs the additional ventilation. This would be based on testing and occupancy behavior. For example, my wife and I live in a supertight home that is way under the minimum ventilation guidelines that I subscribe to, but we have a small footprint on the house as far as vapor pressures, and other indoor air quality issues, so the additional ventilation was not needed. The recovery ventilators will save some energy, but the energy it is recovering is offset by the additional air flow that was created by the system. There is no point in creating more holes unless you need to.

Thank you! It really depends on the house for me as far as complexity. I do see your point, but material cost is an issue, and rental of equipment for homeowners. Having said that friction fit rigid board foamed in is my preference, there is certainly nothing wrong with going with spray foam, if you prefer.

Thank you. The bath fan rule is very general, but basically you do not want excess moisture in your home. Having said that, too low a humidity can be bad also. Here where I am in PA, that is never a problem, we are trying to keep moisture out and humidity low, otherwise the indoor air quality is adversely affected as well as the durability of the structure. It really depends on what climate you are in and what season it is as far as what the humidity should be. In Minnesota for example a relative humidity of 25% is appropriate in the winter, but in Cincinnati it would be 35%. I would be concerned about adding moisture to the house through the bathroom as it is very localized. If you don’t have any mold developing, you are probably fine as far as too much moisture is concerned. If you want to add moisture, than house plants put out strategically can do that, but just be sure that you do in fact need to raise the humidity.
I would only rip out the rock wool if it is wet, otherwise it should be fine. I would insulate the attic floor provided that is your thermal barrier. I am assuming the attic is not part of the thermal envelope, and the ducts do not run in the attic and it is unconditioned, otherwise it would be awfully expensive to spray foam the rafters.  

Your welcome! In regard to the window setup from the website you referenced, they function similar to storm windows, which are effective retrofits. New windows are too expensive, but this setup may work. Below is the math required to find out how many BTU’s you can save with this retrofit. So simply figure out how many FRN’s you are saving based on your fuel source and price of the source compared to your cost for the retrofit, and you can decide if it makes sense.
The U value of the windows (Which is 1/R)  X Area X Heating Degree Days x 24= BTU’s transmitted annually across the surface
Your current setup- .5 X 100 FT2 (my guess on area jusf for calc.) X 7511 (Portland Maine) X 24= 9,013,200 BTU’s if propane heat, that is 97.96 Gal.
The New setup- .25 (R-4 instead of R-2 per website’s claim) x 100 FT2 X 7511 X 24= 4,506,600 or 48.98 Gal.
So 49 Gal’s of savings would be $171 at 3.50 per gallon. At 3$ a ft2 installed that would be a 57% ROI.
The hot water heater would not have a major effect on your heating load. I understand what you are saying, and it is true to a certain extent, but that heat in your furnace room is probably waste heat anyway. That really should not be a concern, but you could ask the manufacturer to be sure. For me it has never been an issue. You might get a slightly lower ROI because you only have a 30 gallon tank, my calculation was on replacing a 50 gallon.
Keeping a relative humidity below 50% in the winter and 70% in the Summer will help minimize condensation, fungi growth, and dust mite populations.

Just want to say this was an absolutely awesome freakin’ post.  This page is going to the top of my priority bookmark list, and I’m also sending this immediately to my folks.  Unlike me they own their homes, and I think this may finally get one or both of them to take that important first step.

  • Nickbert