Follow the construction of Tom's super-insulated home in Port Townsend, WA

Saturday, October 15, 2011

Siding, Paint, and Solar Panels

My initial plan was to put cedar shingles on the whole house. That plan ran into several snags: 1) Shingles are made from old growth cedar and plastering old growth wood over my house didn't seem like the right thing to do. 2) I wanted to see the wood grain through the finish which means that I woud have to use a transparent or semi-transparent finish. The people at Miller Shingles in Granite Falls told me that going that route, I'd have to refinish the south side every 3 years and would eventually need to put on a solid stain to hide the blemishes. That sounds like too much work. So I went with Hardie boards and planks. They are made from cement and fibers, take paint well and last forever. Glo and I played with color samples and patterns for a while with Jesse's help and finally decided to break up the wall area by using a board and batten pattern on the ground floor level coupled with 7" sidings above. We also decided to use a single color for both areas with a separate lighter trim color. Here are the results on the south and west sides.

The south view also shows the 3.1 kW photovoltaic array on the dormer. I hadn't planned to do this, but the incentives from the electrical utility and the IRS are quite attractive: there is a tax credit for 30% of the purchase price (which was $30k) and I get $0.54 for every kilowatt hour produced because the panels and inverter are manufactured in state - even if I use the electricity generated rather than dumping it in the grid. With those incentives, I should be able to pay off the purchase cost in 10 years. The control panel on thenorth side of the house is pretty ugly, but we'll cover it up with artwork further down the line.

For my sister Carolina, pictures of the kitchen granite counter.

What a relief to have the outside (almost) done just in time for the rainy season. I still have to put cedar shingles on the north side porch. I've stained them all and will get started on this project next week. In the meantime, there have been lovely meals outside, enjoying the view to the south.

Friday, June 3, 2011

First pictures of the interior

Two postings in one day! Gotta catch up. I moved into the house on May 1, which was 8.5 months after excavation started. The last phase went slowly because Charles was no longer working on the house, (because I needed to save money) and I divided my time between building and writing on the new edition of my physical chemistry textbook.

The ground floor has the kitchen - dining - living room on the south side, going from east to west. A workroom/studio, a bathroom, and the media room/guest bedroom are on the north side. If needed, there could be 2 bedrooms on the ground floor. The pictures below show the kitchen-dining-living areas. No handles on the cabinets, and no art on the walls yet. More pictures of the other rooms in a later posting.

Here is the stairs going up to the second floor

The bedroom, two office areas, the laundry area, and a second bathroom are on the second floor. The picture below is of the bedroom and the door goes out to a small west facing balcony. Pictures of the other spaces in a later posting.

The energy recovery ventilator

 I've been really busy working on the house, so no postings in a long while, but now I'm back!

A passive house is practically airtight, so a whole house ventilation system is needed to assure the indoor air quality. Quoting Wikipedia, "indoor air quality can be affected by microbial  contaminants (mold, bacteria), gases (including carbon monoxide, radon, volatile organic compounds from rugs, furniture, paint, etc. ), particulates,  or any mass or energy stressor that can induce adverse health conditions. Indoor air is becoming an increasingly more concerning health hazard than outdoor air. Using ventilation  to dilute contaminants, filtration, and source control are the primary methods for improving indoor air quality in most buildings." Generally the outdoor air is healthier than the air in your house. For residential use, 60% of the air in the house should be exchanged with fresh air every hour. However, if the exhaust air is at 68 F and the incoming air is at 40 F as is typical for the winter in Port Townsend, ventilation results in an appreciable energy loss. The remedy is to use an energy recovery ventilator.

The heart of an ERV is an enthalpy wheel shown above. It is a wheel of about 20" diameter and is divided into pie segments. Each segment is both an air filter and a heat storage medium. In the picture, the warm exhaust air goes through a pie segment and transfers heat to it so that its temperature increases. The wheel turns, and the warm segment is now in the path of the cold incoming air. In passing through the segment, the air is warmed up and the pie segment is cooled. Pretty simple heat exchanger: the air exiting the house gets cooled before it leaves, and the incoming air gets warmed before it is distributed in the house.

I used a Recouperator made by Ultimate Air, which claims an efficiency of 90% - that is, 90% of the energy in the exhaust air gets transferred to the incoming air.  The picture below shows the unit (second picture).

The aluminum foil covered box to the right bottom brings in the incoming air. It is well insulated to keep from cooling down the mechanical space. The vertical black pipe on the right goes to the exhaust vent on the outside of the house. The black flexible ducts on the left of the unit bring exhaust air into the unit and send air out into the house. 8" ducts necking down to 6" ducts pull air out of the kitchen, 2 bathrooms, and the laundry area. Corresponding ducts send air into bedrooms and the living room.

The top picture shows the "furnace" and is the only heating unit in the house. It is a galvanized box roughly 20" x 10" x 10" which contains a 2.5 kW heating element. The tan box in front f it contains control electronics. By comparison, a typical oil filled radiator is rated at 1.5 kW.  The good news is that this is a pretty small furnace. The bad news is that this is a pretty small furnace. It takes about an hour of operation to heat the house one degree Fahrenheit. That is OK if the heating is under thermostatic control, and my thermostat can be controlled remotely over the internet. So, on the way back from vacation, I can bump up the heating the day before I get home. In the normal ventilation mode, the ventilator blows ~ 60 cubic feet per minute (cfm) of air through the house. In the heating mode, the blowers are bumped up to 200 cfm. In the ventilation mode, you can hardly hear the unit. In the heating mode, it is audible, but not loud.