Making Homes More Energy Efficient

The auditor came well recommended and runs the largest home energy audit firm in the area. State of Maryland found an average savings of 20% from energy audits in this area. My calculation of 11% is slightly conservative, as it takes a category of "20% or more" and counts it at 20%. Ours is a well-to-do and enlightened congregation, and the subsidized rate may have encouraged individuals to take the audit just to verify that there was no low-hanging fruit. All told, the results looked about right to me.

If the candidates for auditor here had claimed an average 50% savings, I would have demanded documentation in the form of pre-post comparison of utility bills. None of the firms we interviewed here claimed typical improvement anywhere close to that. That must be a Maine thing.

 

My windows have the older aluminum exterior storm windows. Are the interior storm windows better than the exterior ones?

 

Interior storms are not really any more efficient, it it just that it is easy to build removable interior storms since they don't have to send up to the weather. If you have aluminum storms now,, there is no reason to change them, assuming they don't leak too much air.

A little known fact of glass, is that the R value of the glass is self is nearly zero, ~R1. Add an extra pane of glass and you double the insulation value to ~R2, but it is not the glass that provides the insulation, but rather the trapped air space between the two panes of glass. Additionally you cut down significantly on infiltration with the extra layer. They hype with triple glazings and exotic gasses in windows is almost smoke and mirrors. Adding a 3rd layer of glass further increases the R value to ~ R3, which may sound like a lot, but when you consider that a 2x6 conventional wall sitting next to the window will be insulated to better than R20! (the ceiling should be closer to R40. I tell clients, that instead of spending the big money, beyond double glazing, they would be m ch better off to spend the same amount of money adding insulation ithe ceiling,, or the walls.

Icarus

 

Actually, the interior storms I recommend are double (or triple) pane in themselves, This adds R-2 or R-3 to existing windows. Furthermore, the are framed in wood, not Aluminum (which they use to make pans since it is such a great conductor of heat). If you have Al triple tracks, you can leave them on, but add interior storms and see a significant improvement. The materials can be had for around $1 per square foot, so the payback is under 4 years for even the best double pane windows.

[note: when making sure your Al storm don't leak too much air, don't block the drain holes at the bottom. Those are necessary.]

Comparing windows R-values to wall R-values misses a vital difference between the two. Windows admit light and heat into the building. A good window can be energy positive, adding more energy to the building than it loses, something a wall can't do no matter how much insulation it has. Really good windows can now be had with R-values in the 8 to 9 range (while still having high solar gain (for those that want that)).

Having energy efficient windows has another benefit that is rarely considered; they don't condense humidity. A under performing window which experiences condensation is losing energy when the water gives up its vaporization energy (to the tune of 970 BTUs per pound). Plus you get water where you really don't want it, i.e. ruining the seals on your expensive glazing units.

Of course, this is not to say that insulation isn't useful as well. R60 all around is the simple rule we use for around here.

lo-e coating actually is a mirror (very thin), but I don't think I would call Argon, smoke.

 

Nice! Much better in the long run that sticking the film directly to the window frame or wall.

If you have cat that likes to scratch at windows when it sees critters outside, the film doesn't last very long though

 

Could be.

We see people with $5,000 per year heating bills around here.
On the other hand, a efficient house might be around $600. That is a lot of variation. As this is for 7500 Heating Degree-Days, if you in Maryland (around 4500 HDD?) are seeing bills in the $300-400 range you are probably good.

 

True enough. The film is pretty forgiving of blunt trauma, but anything sharp will make a tear. I have actually not heard many complaints about cats shredding interior storms. Though of course, it could just be that people are patching them and not mentioning it. Or the complaints just aren't making it back to me. I estimate that around 5,000 of them have been made in Maine (mostly by the homeowners, or church groups, and other volunteer organizations like Habitat for Humanity).

 

The ones I saw torn were in my son's living room where he has floor to ceiling windows the length of one wall, so it was an extreme case.

 

One insanely simple thing is to put proper awnings over sun exposed windows on the outside of the house.

 

Corwyn,,

Clearly you know your stuff, congrats. I would add a couple of things. Windows can (and do) add to solar gain in the heating season, awnings and shade trees can and do counteract that in the cooling season if you have one.

Windows can also be made much more efficient with the use of night insulation,, either window quilt material, or pop in insulation panels etc, often that come with a much lower cost per square foot (and higher R value gain!) than do exotic, expensive windows themselfs.

I live part of the year in sub arctic Canada, and we routinely have -40 winter temps. We hav built simple clear plastic storms that install out side and make a huge diffence, and dramatically cut down on moisture on the glass. We also use window quilts when it is very cold, but since the house is only 350 sq ft, and we heat with wood, too warm inside is often a problem when the temps get closer to 0f.

Bottom line, there are lots of ways to skin the cat,, and most of it is all good.

Icarus

PS I use, and still use the heat shrink 3M window kits. If you are careful you can remove it in the spring, and reuse it year after year.

PPS. It should also be noted that proper site design, south glazing to help with solar gain during the heating season, proper overhang length to reduce gain in the non heating seasons, proper plantings to shade in summer, but allow sun in the winter. Good design, even using conventional technology can have a huge effect on energy consumption. Even older houses can benefit for passive solar gain if you look carefully at it.

 

If you live in a hot climate and you are considering repainting outside please check out the new heat reflective paints on the market now.
http://www.astecpaints.com.au/enery

 

I had 29 solar panels put on my roof in november. So far these have generated just over 3000kwh of electricity....$600 worth at the meter. but in energy credits (srecs) they have generated another $1500.
In conjunction with this I had to have an energy audit completed, which discovered real problem areas in my ductwork, and inadequate insulation. and I was able to receive a grant for roughly $1800 of the $2000 in work I had done.
Federal tax incentives(30%) and state incentives in many states, coupled with SRECS make the payback on solar under four years!

Otherwise, the simplest change that we can make in our homes are CFL's...and....HANGING A CLOTHESLINE! I hang out two loads of laundry a week, pretty much year round. My clothes smell better, the house doesnt get as warm, and it saves more than a buck a load. The US leads the world in clothes dryer ownership, in most countries people still hang laundry.

 

Every house is different with different weaknesses. A good audit will identify the key issues for your specific house. I was able to design my own house and make it efficient from the start, but I also added some retrofit tips to my web site - Westbrook House

 

very interesting reading about your house!

 

I have older home with thinner double pane windows. Instead of hugely expensive window change, not recommended as cost effective by the audit, I put in the tracked, insulated, up/down blinds. Can let in light during day while up and adding a lot to the insulation of the windows. Half up at the top to block sun in summer. Or half up at the bottom to let in sunlight in winter and give some insulation at the bottom.

 

Aside from inadequate insulation and draft sealing, my inspector found my main heating/cooling duct in my attic was split. The guy came down shaking his head "you've been pumping all your heat and AC into your attic...probably for years".

 

Insulated duettes can be had with quadruple pleating with an r- value of better than four, add that to an r2 window and. U hve a reasonable r6 in the window, open to let solar gain in, close to reduce heat loss. The tighter fitting the better to avoid convection loses.

An interacting side note, a pane of glass gets virtually all it's r value from a thin film of static air on both the outside and the inside of the pane. The slightest breeze on either, or both sides wil effectively reduce the r value to near zero! So obviously wind on the outside is a factor, but draft from HVAC can work to decrease the efficiency of the window system. That is why window coverings, even simple curtains are a must in cold climates. The more the better, right up to an r20 piece of thermal covered with cloth if you wish to go whole hog!

Icarus

 

I want to emphasize the "tight fitting" aspect. Without a tight fit what happens is the windows get cold (as expected) the air behind the shade gets cold and sink out the bottom and is replaced by warmer air. This is effectively a heat pump, moving heat from the house to the outside. Furthermore, once the window gets cold enough to reach the dew point of the inside air. The warm air will also be dropping moisture on it way through. This means you will be losing the heat of vaporization of water as well (970 BTUs per pint of water, as opposed to 0.018 BTUs per cubic foot of air per degree). This could completely offset any saving you have from increased R-values.

 

Inside vertical surface (presumed still) air layer = R 0.68
Outside surface (presumed 15MPH wind) air layer = R 0.17

For those that care about the numbers.

 

Anyone, or know of anyone, that has put up a windmill (for electricity, not water) for home use?