Going solar in Stevi on Habitat home

By Michael Howell

The new home being built by Habitat for Humanity in Stevensville sets a new benchmark for the non-profit organization in its efforts to build affordable homes for low-income people in the valley. Besides keeping the cost down through generous donations of materials and labor from local companies and individuals, the latest home going up in Stevensville will also continue to save the homeowner money down the road by reducing heating costs to almost zero.

The low energy cost for heating has been achieved through a combination of active and passive solar design. The design was created by local architect Meghan Hanson of Natural Dwellings Architecture in Stevensville.

As Hanson explains it, the home is elongated on the east-west access, allowing for a longer south elevation for larger windows to bring in the sun. The heat from the sun is passively ‘collected’ in the concrete slab floor and helps to heat the home. Minimal windows on the north elevations will help mitigate heat loss.

The design allows for almost double the insulation value of a normal home. It features a double stud wall which is one foot thick and full of blown-in cellulose insulation (recycled newspaper). In addition, rigid insulation has been added on the outside of the sheathing as a thermal break to create a very energy efficient wall system. A home built to code must have an insulation value of R21. This home will have an insulation value of R56, more than twice the required R value.

The roof is a prefabricate truss with a raised heel which is a very economical roof that allows room for a lot of insulation. The roof will be insulated to R80, code is R49.

According to Hanson, the floor plan is designed to maximize the use of a small space. Living areas are on the south with bedrooms and bathrooms on the north. A mechanical room is centrally located within the thermal envelope. A central dropped soffit runs the length of the home allowing for easy ventilation access to all areas. This is below the truss roof so that a good air barrier can be maintained in the ceiling. Windows will be triple-glazed.

“We modeled the home in two different computer programs to help with the design,” said Hanson. “The first allows us to test the solar angles at any day of the year in this location. It helps us to design the overhangs to properly shade in the summer and allow the sun in during the winter. The second estimates the mechanical heating and cooling loads for the home. These are much lower than a conventional home due to the passive solar design, and well insulated/sealed envelope.”

Hanson said they intend to perform a blower-door test on the home once the windows/doors are in and it is insulated. This tests the air tightness of the home before the drywall is installed and allows for areas that may have small areas of air leakage to be sealed up. Attention is paid to every detail in this regard, such as the flanged electrical outlets that allow for a tight, insulated seal.

Because the home is small, passive solar, and well insulated, it can be heated with a mini-split, that is, an air source heat pump that is very efficient.

To top it all off, an array of solar panels has been mounted on the roof that will produce up to 7 kilowatts of power and be tied into the grid.

“This will mean that the homeowner’s monthly heating/electric bills will be very, very low, or nothing!” said Hanson.

The active solar installation was made possible by a grant from NorthWestern Energy and a lot of volunteer labor by Dan Brandborg, of SBS Solar in Missoula. The list of local companies donating materials and labor or providing it at cost is impressive and includes Donaldson Brothers, Beck Builders, Fisher Family Construction, Western Building Center, Massa Home Center, The Plumber, Sapphire Electrical, Turnkey Construction, Soapy’s Excavation, Sweet Pea, Bitterroot Disposal, the Senior Center, Dom Florian and Ed Cummings.

As foreman for the project, Rick Wiesmann is fond of pointing out, the low cost homes being built by Habitat for Humanity are made possible not only by the local companies contributing to the cause, but by many, many hours of volunteer labor by local citizens. Some of the most notable volunteers, because they are the most constant and reliable, include Charles Renner, Tom Hanson, Brad Pollman, and Tom Galagher. Volunteers need no special skills, but any special skills are appreciated. You simply have to show up on the work site at 105 Mission Street in Stevensville between 9 a.m. and 4 p.m. on Friday or Saturday and you will be put to work. A bag lunch is provided by members of various churches in the north valley.

“Volunteers can work for one hour, or for several hours, every Friday and Saturday,” said Wiesmann.

A Pint Night fundraiser for Habitat for Humanity will be held on November 24 at the Blacksmith Brewery on Main Street in Stevensville from 3 to 6 p.m. There will be a split-the-pot drawing, music and a silent auction.

Next spring the organization plans to start work on a second home right next door to the one being finished. Prospective homeowners may sign up for consideration starting on December 1, 2013. The sign up period will last for 90 days. Interested persons should contact Habitat for Humanity at 375-1926.