Question

I'm developing a wooded property on a small lake for a retirement home. What green features can I build in that will get the best payback?

Asked by Tara Goci
Rochester, MI

The front of the house may face south. Can I still have passive solar and still have an attractive entrance? What about geothermal heating/cooling? Also wondering about using rainwater for inside and outside uses.

Answer

William J. Martin, AIA, LEED AP-H

Answered by William J. Martin, AIA, LEED AP-H

Westwood, NJ

WJM Architect

September 27, 2010

I would try to incorporate as many green home design features as possible, and here's why:

You stated this would be a retirement home. If you plan to live there long term, you will want to keep your energy bills as low as possible. Reducing energy usage will also likely have the greatest benefit to the environment.

Insulation and Building Envelope

Choosing the best insulation is the key to reducing energy usage.

You might want to use structural insulated panels (SIPs) as a wall system. These panels are constructed from expanded polystyrene insulation, sandwiched between two 1/2" sheets of oriented strand board (OSB). They provide excellent insulation, are very strong, and eliminate the thermal bridging problem of wood stud walls. Check out the Panel Pros website for examples of SIP construction.

Insulated concrete form (ICF) or precast insulated foundation and insulation placed under the basement or crawlspace slab can reduce heat loss into the earth around and below the house. Try Superior Walls for more foundation information.

I recommend a roof truss system with a closed cell spray foam insulation sprayed under the roof surface for a thermal roof barrier of R60 or higher insulation value.

Triple-glazed windows (see Harvey Building Products website) will allow for daylighting of the interior while reducing heat loss in winter. Exterior doors should have proper flashing and interlocking weather seals to reduce heat loss.

Ventilation System

Once the house is correctly insulated, flashed and sealed to prevent any air drafts, the next consideration would be heating and ventilating systems.

With an airtight house, you will need a fresh air filtration and air exchanger with an energy recovery component to bring in ventilation air and bring it up to temperature by exchanging heat with the expelled air.

Geothermal

You mentioned a geothermal heating and cooling system. I am a big fan of geothermal systems. Geothermal systems can also be used to make hot water.  A couple of issues in deciding about geothermal:

  • Your site is lakeside or near a lake. Geothermal systems can be drilled as vertical wells or set under the ground with buried coiled tubing to exchange heat.
  • You should have a professional check your site. If bedrock is close to the surface or there is unusual hydrology, there may be some difficulties that drive up installation cost or prevent efficient operation.
  • Try the GeoExchange website for information on geothermal.
  • Another comment about geothermal. A geothermal system is usually connected to a heat pump that draws out the heat in winter and pushes out the heat in summer for cooling. This heat pump is powered by electricity. If you really want the efficiency of this type of system, you should consider active solar power in your design as well. Photovoltaic solar panels can generate electricity to partially power the heat pump during the day.

Siting and Passive Solar Design

You mentioned your site is wooded. If your site is heavily wooded, solar energy, whether passive or active, may cause you some significant tree removal issues. Plan out the location of your home with this in mind. I would recommend you minimize tree removal as much as possible, for both cost and environmental reasons.

You also asked about passive solar and the aesthetics of your home entry. This is a matter of configuration and architectural design. A creative, AIA green architect can design a passive solar home configuration with a unique and beautiful front approach and entry.

Rainwater Collection

Next, you mentioned rainwater collection. Rainwater collection can be done for inside and outside uses. Irrigation of gardens and landscaping works well from collected rainwater. Rainwater collected can also be adapted for interior uses such as flushing toilets or clothes washing. One way to do this is for your roof gutter and leader system to channel the rain into an underground tank that would have a pump or pumps to distribute the collected water to where it is needed.

Inside the house, this is done through a distribution system that is separate from your potable drinking water system. You should be aware that some states prohibit rainwater collection systems, particularly in the western states, because of aquifer recharge issues and water rights.

 

Aesthetics

To me, the important thing is to carefully integrate all the building components and functions. Draw aesthetic inspiration from the site and the integration of these components to create the beauty of the house. If done carefully and thoughtfully, this will create a balance between aesthetics, function, and economics that will be harmonious.

This does not mean the house has to look strange or ultra-techno-modern, unless you prefer this. I believe this can be accomplished in a number of styles and can fit into the local vernacular architecture of the area.

Return on Investment

Finally, you asked about payback cost. Payback cost, or "return on investment" (ROI) can be significantly different depending on your location. I recommend you ask local suppliers of these systems what the current ROI is for the various components you are considering.

You stated this would be your retirement home. If you plan to live there for a long time -- and I wish you a long and productive retirement -- the energy savings from these various systems will create a positive ROI at some point. It is only a matter of time before the energy costs saved pays for the cost of these systems.

Also, in my opinion, reducing energy usage will have the greatest benefit to the environment.

 

For more information:

Read Polly Osborne's Q&A "How much does green construction add to the cost of a new home?"

Tagged In: green cost, sips, geothermal

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