A Story Of An Off The Grid House
The ‘Off-the-Grid House’ in Litchfield County is all but done! The house and farm were selected to be on the Goshen Farm tour again this year and it was all just so beautiful. The house itself is a long stone structure facing south. The core exterior walls of the house were actually built using Durisol (a form of Insulated Concrete Form (ICF) but are made from natural fibers instead of the usual foam.) covered in stone veneer.
The house is designed to be a Passive Solar house – in the old school way. (It was not certified Passive House, though I personally believe that if it was modeled and tested it would meet Passive House standards). Anyway, in old school Passive Solar design the idea is to build a house to face south and provide a lot of thermal mass within the house. The house warms up during the day and the thermal mass (usually concrete or stone) holds the heat and slowly releases it through the night. The whole thing is dependent on specifically designed overhangs curtains and fans to keep the sun in the house when it’s cold and out of the house when it’s warm.
This entire house is bermed into the ground on the long North side (to about 8’ high).
The long South side of the house is all windows (lower sliding glass doors and upper transoms) with overhangs that were very specifically designed to let the winter sun in and keep the summer sun out.
The floor of the house is concrete over about 11” of rigid foam insulation board. And the back wall of the house is about 14’ tall and all stone. The floor and the back wall of the house are the thermal mass. They collect the suns warmth. (The floor gets the sun through the sliders, the wall gets the sun through the upper transoms.)
The green house along about 1/3 of the south side will not only serve to grow food year round, but it also acts as a heat collector and buffer that allows the home owner to control the amount of heat in or out of the house.
There are ceiling fans throughout the house as well as operable transoms that allow for a great breeze and air exchange during the temperate months. During the winter the house will use Lunos ERVs. Small super-efficient air exchangers.
There is a lot of insulation in the house. About 18 inches of cellulose in the roof for a total of about an R60. The 11 inches below slab XPS foam adds up to an R60. The exterior walls (Durisol plus stone veneer inside and out) add up to about an R28, however they are extremely well air sealed and about ¼ of the exterior walls are buried in the ground- which up the R value exponentially! The windows are all Klearwall Passive house level triple pane windows and doors. (Approximately and R7 or R8.)
The house is heated only by a wood furnace that is kept in the back yard. There is a wood burning cooking stove as well inside the house which will also serve as a heating element. The fact is however that either of these will quickly over heat the super insulated house and will rarely be needed. There is no active cooling besides the old fashioned open windows and ceiling fans coupled with cool summer time concrete and stone.
The whole house is off the grid. The red barn on the property has a 10 kW PV array that serves all of the 2,000 sf house’s needs.
There is a root cellar along the back (North) bermed side of the house. It is basically a concrete and stone box. The floor is concrete with no insulation below. The two walls it shares with the main house are the insulated Durisol and stone walls. The other two walls and surrounded by earth for their full height. The roof has about 12” of insulation (foam) and is then covered with dirt. It all stays very, very cool (about 55 degrees) – even on the hottest days of the year. (There are no active vents in this root cellar. It seems to be working very well without a vent, though the home owner is keeping an eye out for moisture build up, it does not seem to be an issue.
All of the water from the house gutters and from the footing drains is collected and directed to a site built pond on the lower portion of the site. This pond will serve as watering hole for the farm animals.