Solar advice to a friend building a new home

Here are some notes I wrote up for a guy I know, a Unity alum and parent of a Unity student, who is building a new home for his family.

XXXX, you ask for some thoughts on reviewing the pictures of your site:

1) In general, solar energy comes in three forms, solar photovoltaic for electricity production, solar thermal hot water, and passive solar which is where we use the sun's energy, and super-insulation and sealing, to heat the home in winter through good design principles and retain the heat.

2) The latter is nearly always the most cost effective way to use solar energy at your stage in the building process. A few extra thousand dollars on insulation and design now can save up to 90 percent of your energy bill later. This is because heat is the largest energy expense for houses in Maine by far, not electricity or hot water. Unfortunately Maine architects are rarely trained in passive solar design principles. Give yours a good interrogation to find out what he or she does or doesn't know. (Those law enforcement job skills come in handy, don't they?) The main features are to orient the longest axis of the house east-west, so the long wall catches the southern sun, and give that wall larger windows, while other walls get smaller windows. If the winter sun is then allowed to fall on massive objects within the room -- usually a dark-colored concrete floor is used as in the Unity House, but furniture and walls can also be used -- then the heat is saved naturally (passively) and released through the night. The house will also be very comfortable and pleasant to live in. Especially if the floor is used as the heat mass. For this to work insulation values in walls need to be R 40 and up and in ceilings R 50-60 and up. Air-tight sealing, including basements, and some form of heat exchange ventilation complete the package. We have such a house on campus, the Unity House and I will be glad to show it to you next time you visit. Just give me some warning. I can also arrange for XXXXXX's class to take a tour. The Unity House was expensive but there are much cheaper ways to achieve the same values.

3) If east west orientation is not or no longer possible, as seems likely based on your foundation pictures, proper up-to-date systems of air-tight sealing and those high insulation values can still save you 70-80% of your heat bill. Make sure to either do them during the construction phase, or at the very least least make the place air-tight now and make provision for additional insulation to be added later (by adding foam board to the outside walls or similar). Use of a blower-door test after the building envelope is completed but before the interior is begun is a good way to assure air-tightness. Insulation is much cheaper than heat bills. Payback for insulation added at this stage, say from R19 to R40 in the walls, is going to be less than two or three years. R40 is not yet standard practice for insulation although it should be. Maine builders are way too impressed with their recent (last decade) code update to R19 code for walls, and remain lazy about sealing basements, although the common use of Typar-type building fabric has eliminated most air links through walls in new construction. Again, interrogate. Don't accept low standards if this is what your builder offers. You need that R40, and you need the building to be sealed. Once sealing is achieved, additional ventilation is needed. It's important to ventilate a tight house properly to avoid moisture problems inside the house, even inside the walls and attic and basement crawl spaces. Powered heat exchange ventilators work best, but careful construction of wall and crawl space areas goes a long way to making sure moisture doesn't end up where it's not wanted.

4) Looking at the pictures of your immediate site, you'll need to cut down a lot of trees to make solar work on that site. Those trees are quite a lot bigger than I thought, and a lot closer to the building. Prove this to yourself next time you visit the site by looking to see where the noonday sun is in December: 23 degrees above the southern horizon. You'll see it effectively filtered through all those trees. The trees will prevent any solar energy making it to the house, and reduce the return on any investment in passive solar design or panels to very little. I would take them all out, if what I wanted was a solar house. No reprieve: all those south side trees that block the December sunpath must go. This stands true for solar hot water too. The only exception is solar PV, where you could locate an array of panels on the far side of the trees and run the power through a wire to the electrical distribution center.

5) If you can get all the above done: design and build a passive solar house or at least a well insulated and sealed house, solar hot water or solar PV is the icing on the cake. It's currently expensive but prices have dropped lately, in the case of PV about two thirds of the price it was four years ago, and in the case of solar thermal hot water about 80% of the price four year's ago. The price is still dropping, and you can get help from the state and a tax credit from the federal government. A reputable installer can design you a system for the house. Here's rough numbers for a conventional two-three bedroom family home: For about $15,000 you can make most of the electrical power you will ever need ( a grid-tied system), and for about $10,000 you can make up to 80 percent of your hot water. Now is the time to go consult the installer, because you want to a) get your taxes back and get the rebates, some of which expire next year, and b) wrap the extra expense into whatever financial instrument you are using to pay for the house. It's this combination which makes it cost effective: the total system will cost $25K, but you get 30% back on your taxes and 30% from the state incentives, so this is only $8.5K, and the payments on, say, an extra $8.5K of financing added to a first or second mortgage are about $70-90/month, which is less than your electricity/hot water bill will be if you didn't have the system. You will still have an electricity bill, but it's likely to be less than $40/month on average, including the cost of making hot water when the sun doesn't shine.

If you don't mind, I'm going to take your name and identifying features out of these notes and post them to my website as an informal guide for students and others to use.

Mick