Solar Power for New Homes
Now is an exciting time to be building a new home. The many energy saving ideas developed over the last 10-20 years have become affordable. Now the challenge becomes picking from the many good options. The different highly insulated wall systems, cellulous, and spray foam choices means that pink fiberglass is a thing of the past. It is now easy to get a tight, high R-value home that will use much less energy that conventional/old fashion construction. The federal solar tax credit and Efficiency Maine rebate program both cover new homes. There are additional incentives to the builder.
This is a good thing for environment and solar energy systems. The better the home's construction, the less energy required. Thus, the smaller and less expensive the solar systems can be. For most home buyers deciding how to best allocate the building budget is a difficult decision. Solar is a major investment, but one that saves a great deal of money in the long run. Unlike fossil fuels, or wood that has to be harvested and delivered, solar generates zero pollution.
In 1 year just 30 tubes can produce the equivalent of 2,256kwh and prevent the generation of over 400K of CO2.
We are not builders, but in the course of our job we see many new techniques and options. If you are thinking about building and just need some direction, or an unbiased source to bounce ideas off, give us a call. We will share any information we have.
The Federal Department of energy has many good publications on building with solar, both for the contractor, and the homeowner,
We are happy to work with your builder or architect to design a system to meet your unique needs.
The 2 panels on the right are solar thermal, all the remaining panels are PV electric. This is a common ratio.
Making a “Solar Ready” Home
If solar thermal hot water and PV are not installed as part of the construction process it is easy and very inexpensive to build in the necessary plumbing runs during construction. This allows considerable savings when solar is later installed.
Important Pre-Construction Considerations:
- PV electric panels must face south.
- Allow a chase way to run the wiring from the roof to the electrical panel.
- Leave room for the installation of an inverter near the panel.
- PV panels will require about 300sq ft.
- Make sure trees and roof lines do not shade the panels.
- Solar Thermal hot water systems like to face south but can be east/west.
- 2 ¾-1inch insulated copper plumbing lines need to run from the panels to the basement hot water tank.
- Solar Thermal panels with 10 tubes are about 7ftx3ft.
- For hot water you need rack 1 per person.
- For heating add at least 60 tubes.
- Allow for a tank with 20+ gallons of hot water storage per person.
We are happy to provide information on “solar compatible” water tanks. These are really rough estimates and we are happy to help you come up with better number if you are concerned about spacing. If you have a large home heating system, additional plumbing may be necessary and you will have more tubes. When grid tied, often homeowners install smaller PV systems that meet only p
art of the needs.
The important point is that it is quite inexpensive and easy at construction time to run pipes and leave a chase way for an electric run. Making a home “solar ready” can give you a marketing advantage when it is time to sell.
Heating Your New Home
Infloor board is quick to install, allows responsive temperature adjustment, works with wood, carpet, vinyl and more.
Radiant floor heat is comfortable and dust free. In the old days radiant was installed in a slab. The idea was the concrete served as a thermal mass. The advantage was that once this large thermal mass was up to temperature, it held it for a long time.
Now the many products such as Infloor and Warmboard give more responsiveness to heat adjustment. Basically these are 4x8 wood sheets with an aluminum layer that distributes the heat from the PEX that is inserted into the pre-grooved slots. They are perfect for areas where you might want to drop the heat throughout times of the day, such as bedrooms.
Slab based systems have an advantage that they put out more radiant heat with lower temperature water. This can be a real benefit when short winter days limit the output of your solar thermal system. Often our customers combine the 2 types, with slab in the basement and 1st floor, and boards upstairs in the bedrooms. Today’s slab temperature sensors reduce the problems with overheating.
Some builders have been known to suggest installing standard baseboard upstairs to save money on radiant. This is a horribly irresponsible suggestion because it requires heating water to 180° vs. 120°. This alone will raise your fuel usage about 15%. Over the course of just a few years you will burn up what little savings you gained on the install.
Protect the Environment and Your Checkbook Balance
Solar thermal combined with radiant floor heat is the ideal way to live. Your system will provide your domestic hot water as well as space heating. In the summer excess heat can be routed to heat your pool for free, or dissipated outside. The size of the system will be based on your family’s hot water needs and the Btu requirements for your home. Once you have your initial building plans we are happy to develop a proposal. An average family can expect to have 3 or more 30 tube collectors and about 200 gallons of hot water storage.
At this point in time, in Maine, using PV panels to provide electric heat is more expensive than using solar thermal.
You will still need a backup system for days when there is not sufficient solar radiation. While cold temperatures do not impact evacuated tubes, during our short days in December and January there just are not enough sunlight hours. Generally we size the system to meet 50-70% of your annual needs (known as the “solar fraction”). This takes into consideration the impact of winter snow and short/low solar radiation days.
Installing your solar system
Collectors are generally roof mounted, but can be ground mounted on a rack, or placed on a secondary building. Generally, collectors work best when facing south. Solar thermal is more forgiving and can face east/west. Collectors need to be in the sun and not shaded by roof-lines. We can provide all the plumbing, radiant and heating products and installation in addition to installing your solar system, or we can work with your builder or plumber.
We have seen beautiful cedar pergolas, window overhangs that also provide summer shading, and railings all done with solar thermal evacuated tubes. In these cases they look like architectural elements, not solar tubes. Velux makes a great flat panel collector. While it does not have the winter output to provide space heating, for domestic hot water it is a great choice if you object to the look of other collectors. Velux’s product integrates with their skylights, having the same size and reveals. They are flashed into the roof for a very streamline look. Output is best when they face true south on a highly pitched roof.
4 Velux solar thermal panels with a skylight at each end.
Photovoltaic (PV) electric systems manufactures are coming out with exciting options. Thin film is said to be they upcoming technology. Right now it is practical for metal roof installations. The thin film is glued to the roof for a visually pleasing look. There are new mesh type PV fabrics that can be shade structures as well as power generators. During 2009 increased competition and global oversupply dropped the cost of standard PV panels significantly. If you have a building site where bringing in power lines is cost prohibitive, an off-grid battery bank system may be the answer. Most homeowners elect to be grid tied to avoid the cost and maintenance associated with batteries. In these cases you pull your power from the grid. You are credited for power created and debited for what you use over a 12 month window. If you have concerns about loosing grid power, you can add a small battery bank to come on in case of a power outage.