How do I figure out which energy improvement to do?

Factual Questions
1

I’ve got a house that’s very similar in style to Eichler houses… in SoCal, built in the late 50’s, lots of huge, original windows, less than 1" insulation in the roof, and a 15 year old a/c system.

Put it this way… A/C runs constantly in the summer and barely keeps the upstairs below 85 degrees.

So I want to do something to make my house cooler, and ideally I want it to be fairly passive (not a new A/C system). As far as I can figure, here are my options, followed by my questions.

There’s not enough space to add insulation inside my roof, so I can

1 - raise the roof and add insulation (very expensive, requires a lot of city hassle to make house 1 1/2 feet taller (height of a joist), but we’ve looked into this as an option)

2 - put a reflective foam roof on top of my existing roof. Doesn’t count as additional height because it’s not considered structural.

3 - add solar panels. Not only lowers electrical cost, but I’ve heard they can be raised a bit off the rooftop adding an additional space between the panel and the roof surface, effectively keeping a pocket of cooler air there (and also keeping direct sunlight off that area). We have a completely flat roof, so this may be easy to do.

4 - Putting strong tinting on our windows (we’re looking at www.solarart.com). We’ve already got some tinting, but this would (in theory) be better.

5 - Replacing our windows with new, double paned windows.

Now my question is, how can I get an idea of how effective any of the above will be? Hard to do a cost/benefit analysis without knowing the benefits. Will tinting the windows more than they are do anything? What’s the best roof approach?

Specifically, I have no way of knowing where the heat is coming in. Are we heating up because of the roof? Or the windows?

Our windows face west (a few on south end as well), and the place really heats up towards the late afternoon, which makes sense as that’s when the sun hits them the most. But it could also be a day’s worth of heat accumulation via the roof. But then again, my son’s room is on the top floor on the north end of the house, and it’s cooler by far than the south end of the house, which once again makes me think it’s the windows.

So how do I figure this out for sure before I spent a small fortune on a major repair? I can probably do one of those, but I can’t really afford two of them, so I’d let to get it right the first time.

And no, the local energy company does NOT do home audits, I’ve asked. They have this cheeseball interactive thing on the web that is so generic it’s completely useless. I need real data on our house and don’t know where to get it.
:smack:

Any suggestions?

2

I’m not sure it’s easy to anything but a WAG around the best ROI. However I’d be inclined to think a good window film with the lowest solar heat gain coefficient would be the best place to start. It seems like it would be the least expensive of the options you mention.

3

Not necessarily looking for the best option from the above, but I’d love to find a way that I can do realistic tests to determine the best option. Are there good measuring approaches I can take to figure this out? I assume salesmen for any of the above options will tout their service over all others, so I need unbiased information. Somehow…

4

Board up your windows from the outside for one month this summer. Then compare the indoor temperatures before and after to estimate the heat gain from the windows.

(Or not.)

5

The answer is not “passive” it’s active. But still a lot better than A/C and that’s fans. They make them cheap and quiet and efficient. Steadily move the air in from the shady side of the house and out the gables. Don’t give the air under the roof time to reach the rest of the house.

6

If you still have single-pane windows, I’d start there. It’s amazing how much of a difference it made for my house both in terms of keeping warm in the winter and cool during the summer.

You haven’t listed it as an option, but have you considered trees and bushes? If placed correctly, they could keep sun off your house during the summer, let it come through during the winter, and serve to beautify the property. This might be cheap enough to do in conjunction with other options.

You might check the phone book for local energy consultants. In the Seattle area, there are dozens who will work with both businesses and homes. Some get paid through commissions on the products they sell you, while others have an up-front fee.

7

Single pane windows are something like R-1. Good double-pane windows are around R-3 (which doesn’t sound like much, but it’s 3x, or going from R-9 to R-27 insulation). Windows are expensive, but they also have very good ROI when you sell the house.

Next, look at doing an infiltration test - tightening up the house can make a huge difference.
Then, add insulation, especially in the attic.

8

Boarding the windows (I’d do a weekend, not a month) is an interesting idea… hmmm. Fans may work, but we’ve got floor fans already. Only do so much.

Trees are no good unfortunately. We’re in a high fire zone and have to work really hard to keep trees away from the house.

We have zero attic, hence the roof option. Inside we’ve got tongue and groove ceilings, with a layer of plywood above, then 1" insulation, then a tar roof. Beautiful to look at, sucks for heat.

Odds are we aren’t selling the house for a long time. I can easily imagine being in this house for 30+ years if we can get the heat under control.

I wonder how to compare windows vs solar power… I’ll see if I can find an energy consultant.

Thanks everyone!

9

My wife does this work for a utility and I’ve picked up a thing or two. I’d say windows first, all the insulation you can manage second, and a white roof third.

Forget about solar. Slanted roofs are superior to flat roofs for them unless you live at the equator. (Think about it. :slight_smile: ) They’re expensive and the payback is on the order of 20 years. For ROI do all the little things first and then the expensive ones.

10

If you want to do an ROI analysis of various energy strategies, most people I know in the industry use the Energy 10 software developed with the National Renewable Energy Labs. You can get more information about it here.

You could also hire an engineer that specializes in energy efficiency to come perform a detailed analysis. A good starting point to find one in your area is the LEED directory here.

Either option will run you a few hundred dollars, but it may be a useful first step before you invest a much larger amount of money in any option.

11
  1. Attic exhaust fan.

I would do the window tinting first and then an attic fan.

12

Can’t do an attic fan. No attic. I’m seriously leaning towards an energy audit, but gonna look into that software, too. Thanks

13

So you have a flat roof like that found in Arizona? You could install a sprinkler system on a timer to cool it off if that’s the case (thinking outside the box).

By the way, you may want to look into geo-thermal now in anticipation of installing it down the road. It makes a huge difference in both heating and air conditioning. I’m kinda hoping the price comes down enough that I can do it myself for the cost of a new heater/air conditioner.

14

Is it possible to just install a roof fan even though you don’t have an attic? You can get one that seals up for the winter months. My office gets super hot due to southern exposure and if I ever get around to remodeling, I’m tossing in an hinged skylight.

Magiver, in SoCal, I’m pretty sure the water shortage makes any sprinkler system irresponsible. However, the idea of a ground based heat exchanger makes a ton of sense, if you’re willing to spend the BIG BUCKS upfront for long term savings for both heating and cooling.

Here’s a cite for the costs.

15

You need not “board up” windows to test them - try putting aluminum foil on the outside for a few days and see what sort of difference that makes - it won’t stop air infiltration, but it will stop almost all heat radiation. Around here people leave the aluminum foil on all summer as a cheap way to make the house cooler, although you do lose all your ambient lighting as a result.

You’d be amazed at what you can discover just by buying a set of accurate thermometers and placing them throughout the house, and then diligently recording the temperatures every hour through the day - repeat for several days, and note the outside temperatures and sky cloud level as well. Make some graphs in Excel and see if you spot trends. If you have some money, get a set of the wireless thermometers with a base station which also measure humidity. You might find such things as “this wall area of the house is always 20F hotter than anyplace else”, or that you have serious temperature stratification and that some indoor air movement might make your AC run less. It’s not super-accurate but it can be a good way to understand a bit more about your house. We have wireless thermometers/humidity meters throughout our house and 6 continuous years of records to correlate trends, and it’s helped us understand the insulation and air leakage problems our house has.

16

As others have suggested, try a home energy audit. ENERGY STAR has a program. There’s a link on that page to local programs.

If it turns out that a new roof would help, try a reflective roofing product. You might also consider installing a light-colored roof, which also absorbs less heat.

You can also try low E windows with argon fill. Don’t know how expensive they would be for you, however. They were beyond our budget when we got an estimate, but I would love to have them.

I know you don’t have an attic, but maybe you could still install a solar fan.