A Personal Journey to a Healthy House
September 10, 2020 by Larry Marner
We just moved in! I call it “House 2” because 22 years ago we designed House 1 in our family odyssey in search of a better environment in which to raise our two children. House 1 was all about expanding into a larger space that living in Manhattan had restricted, a 2-bedroom apartment of 1,200 square feet. It worked. Now, “out in the country” on 13 acres of raw land we thought 3,200 SF would suit us better and in an attempt to make the new abode affordable to construct I reduced the thickness of the exterior walls, used economical windows (in 1996) , had a great fireplace, and designed just what I wanted — a white clapboard house that was a hybrid of an English country home designed by Sir Edwin Lutyens and a 16th century villa designed by Palladio in Vicenza, Italy.
What mattered to us in a house built for the future
We thought that house was beautiful but our annual energy bill for heating and cooling was through the roof. It leaked energy like a sieve like most houses constructed at the time in this area. So, when the kids grew up it was time to move out and try to do a better job next time. We agreed on a much-trimmed down program this time of 1,800 to 2,000 SF. We also wanted to pay much less for energy, “net zero” was the goal. I looked back to our training in the late 70’s to designing with the climate in order to design to the climate and found Passive House.
Passive House principles involve designing a highly insulated, air-tight enclosure that would then use an energy recovery ventilator to provide constant fresh air while expelling stale air and extracting the hot or cold energy at very low cost. It is an all electrical house so we had to say good bye to our much beloved fireplace but that was OK since we would get to live in a healthy house that saved energy and was easy to maintain.
By healthy I mean excellent indoor air quality, expansive windows facing the surrounding forest, stripped-down and nature-oriented. Coupled with a vegetarian diet and running trails close at hand for an easy lunchtime breeze through the woods, the site was ideal for this house concept.
How did the site support new opportunities?
The land we chose had a gradual slope through the woods down to a pond. I recalled the “Mountain House” Mies van der Rohe apparently designed for himself but never built. This long pathway plunging deep into the woods presented an opportunity to situate the house so you could enter it at grade at one end and then emerge at the other end in the tree tops. Deep into those treetops and visible in the distance were the meandering trails through this beautiful 200 acres of conservation land. This house would be designed to step lightly into the forest beyond and involved removing as few trees as possible.
We could orient the long side of the house to the south to capture free heating from the winter sun and with an exterior sun shade, block the sun’s radiation in the summer. A large amount of glass on the south would optimize energy savings, light, and the beautiful views. Then we pivoted to Passive House design criteria to get to “net zero” where the total amount of energy used in a year is equal to the amount of energy produced using solar panels.
Why Passive House?
Passive House is different than many “passive solar” designs where overheating often results. In Passive House the heat losses are balanced with heat gains. This solar access along with a compact form to the building reduce project costs.
A Passive House has these characteristics: 1) Air sealed for durability (most houses are 5 to 10x leakier). This reduces heat loss in winter, reduces humidity in summer, reduces drafts, and eliminates condensation risk within wall, roofs, and floors. 2) Low energy use because they are highly insulated with continuous insulation more than 2x the thermal resistance of a building that complies with the building code. This reduces heat loss in winter, reduces heat gain in summer, and allows comfortable interior surface temperatures 3) High performance windows add more energy to the house than they lose, and 4) Energy Recovery Ventilator (ERV) as a mechanical ventilation system that extracts moisture and heat, then brings in clean filtered fresh air all year round and reduces heat loss in winter.
A “Healthy Building” was a crucial goal
We then went a step further and used Passive House principles and net zero to get to a “healthy building” where we monitor indoor air quality and make adjustments to maintain the highest quality by simply adjusting the fan speed of the ERV or opening a window or two. Temperature, humidity, CO2, and dust are controlled by the Passive House construction details we incorporated.
To reduce the effort and expense of maintenance we painted the exterior with a newly formulated version of the pine tar used to waterproof the hulls of Nordic ships which also has no VOC’s. We were careful to remove only those trees that would be directly in the path of machines used to construct the house. We are in the process of bringing some of the woodland back onto the site. The rest we will plant with a matrix of perennial planting, a potager’s garden, and no-mow grass.
The drive to Net Zero
We are waiting to see how much electrical energy we use before we install solar panels. We estimate we will use 6,000 kWh per year. This will require an array of panels measuring 400 SF and we have reserved the location and the wiring for it to be installed once we measure the actual use for a year.
I’ll have more on this in the future as well as how we measure indoor air and water quality to maintain a healthy building.