Archive for May, 2011

Spinning backwards

We did a short test run of the solar system yesterday and generated our first kilowatt hour* (kWh) in about 20 minutes. It was very satisfying to watch the meter spin counter clockwise. It was an overcast day, but the system was still producing anywhere from 2.2 kW up to 4.8 kW.

We had to shut it down after the test because we don’t have a bi-directional electric meter from the power company yet. Without it they would charge us for both the electricity they provide us as well as the electricity we provide them!

* 1 kWh will power ten 100 Watt bulbs for 1 hour.

Mechanicals rough-in

Our mechanicals contractor started roughing in the duct work for the ventilation system last week. If you recall my earlier post, Mechanicals (ERV and ASHP), I tried to model all the ducting to anticipate the problem areas.

Our installer, Phil, has been installing ventilators and air-source heat pumps for quite some time, and he has brought a lot of experience to the table. This will be essential in some of the tricky spots. Out of the four areas I was originally worried about, only one has Phil mildly stumped; connecting the outside air ducts to the ERV.

Determining how to orient and position the ERV in the basement in order to minimize the number of twists and turns is a real challenge. I don’t think we’ll actually know the final configuration until the unit arrives in a few weeks.

I’ve also been a bit concerned about the number of T connections that Phil has been using. My research has led me to believe that these should be Y connections. T connections impede the flow of air. Phil assures me that this is not an issue considering the relatively low air pressure in the system. I remain skeptical, but relented as long as the required air flow at each register can be achieved.

Lessons learned: I should have located the ventilator somewhere on the first or second floors instead of the basement. This would have greatly simplified connecting to the outdoors, although it would have brought the unit closer to the living spaces and potentially caused a noise or vibration problem.

I also should have moved a few walls so that they did not sit directly on top of a truss. Trusses are wider (3.5″) than normal joists (1.5″). This makes it extremely difficult to get vents and plumbing stacks up through these walls without some gymnastics.

I’ll add more details when the ERV unit arrives onsite.

Now that’s a roof!

We’re just a few steps short of generating power for ourselves and sending the extra back to the grid. The panel installation on the roof and all wiring is complete. All that is remaining is a final electrical inspection (for the solar portion of the electrical system) then a visit from the electric company to replace our meter. Hopefully all this should be completed in the next couple of weeks.

It’s a dirty job…

I’ve noticed that we’ve somehow avoided talking about two of our most important and time-consuming chores: Moving stuff & construction clean-up.

Supplies, tools, and mountains of siding are being stored in the house. This stuff periodically needs to get shifted around from east side to west side and from 1st floor to 2nd floor to basement to access various areas of the house. Hopefully this will take up less time as materials are used up and the siding is installed.

We also spend a few hours each evening sweeping up of an endless supply of sawdust, dirt, scraps, and ladybugs*.  Not only does it make the house safer and more enjoyable to work in, but we’d rather have the professionals we’ve hired to help us concentrate their efforts on the tasks at hand (electric, plumbing, insulation, drywall) instead of spending their time (and our money) doing grunt work. We love the Shop-Vac we bought a few weeks ago. It’s by far the best way to clean out between the double wall framing. Why did we wait so long!

We’ve also taken on sorting trash and making dump runs. Our transfer station only charges for landfill garbage, so we save money and help the environment by recycling as much as possible. We’re still on our first box (30-count) of 42-gallon recycled, oxodegradable contractor bags, using only 2-3/month, so we’ve been pretty good about keeping waste to a minimum.

* A swarm of ladybugs moved in before we closed in the house last fall, hiding in the framing and under stacks of wood. Every warm day some wake up from hibernating and crawl/fly about before dying. Once the house is air sealed, they won’t be able to get back in, but does anyone have any ideas on how to get them to move out?

Solar: 2 down, 28 to go

It rained most of the day, but the solar guys managed to get 2 panels up.

Foam continued…

While the solar installers have been on the roof, Warren and I have been in the basement foaming the rim joist area. We are foaming this area for two reasons. First, we need to seal the water proofing barrier to the top of the concrete wall. The water proofing is also our air barrier and keeps any radon gas from seeping out at the top of the wall. Second, this would be a difficult and time consuming area to staple up a net and blow cellulose.

Here’s the rundown on our approach.

  • We’re using a two part foam made by Touch’n Seal. They make standard and fire retardant type foams. We’re using the fire retardant type because we’re not planning to finish off the basement ceiling any time soon.
  • We are foaming this area to a thickness of 7 to 9 inches to ensure we meet our stated R40 minimum. The foam is rated at 6.23 R per inch for the fire retardant type. The R value is a bit higher for the standard foam.
  • We’re using the 600 board feet kit. It includes two tanks, A (white) and B (red). We bought the longer hose set, 30 feet. There are 2 hoses. The liquid from each tank is combined at the nozzle where it combines with air to create high expansion foam. The nozzles are replaceable. We’ve used quite a few as the foam clogs them easily.
  • The temperatures have been in the 60’s and 70’s, but the foam really works best at higher temperatures. The tanks should be at 80 to 90 degrees before use and the surface temperature where you’re spraying should be above 70 degrees. Warren built a foam box that we use to warm up the tanks before use. We dropped in a small electric space heater to get them up to the required temperature range.
  • There’s a bit of conflicting information as to the surface temperature. We asked because we were experiencing some shrinkage away from the wall. The foam would expand initially, then pull away from the wall slightly as it cured. It only takes few minutes to cure. But the second and third sprayings seem to be doing a better job. The first application pulls away a bit, then provides support for the next application, holding it in place better. Our last spray day was quite warm out, but the higher surface temperatures didn’t seem to make a difference.

We’ve used 3 kits so far and have covered the attic rim area and half the basement rim area. We’re guessing we’ll need a little over 2 more kits to finish the basement and foam the north and south rim joists at the second floor. The east and west rim areas at the second floor are easy enough to net and blow cellulose.

Lessons learned?

If we had hired a professional crew to come in and spray all the areas and I wasn’t there myself watching the process, I might think this was the best stuff in the world. But having gone through the process of doing it ourselves, I would absolutely not use this much foam again. I’m so glad we decided against the ‘flash and batt’ approach. This stuff is nasty, and we can’t even recycle the containers. The instructions that come with the containers didn’t even mention using air breathing masks. We had to call the company to get a recommendation on the right type of mask to use. Get one that blocks organic compounds and make sure you have plenty of fresh air while working.

I knew the foam was not a green product, but I was willing to trade the hazards for the long term benefits of a more air-tight, super insulated envelope. Now I’ve changed my mind. A little foam in strategic spots is fine. But if I design another home like this I would go out of my way to find other solutions.

Just as I was putting the finishing touches on this post, the always timely GBA posted this article, “Waiting for EPA Action on Spray Foam Insulation“.

First panels arrived today!

Despite the weather forecast, it was a beautiful day and the solar guys were able to finish installing the clips and rails and get everything wired up. If it’s clear tomorrow we will finally see the first panels on our roof!

I also met with the HVAC guys from Dee’s Electric today. We walked through the ventilation ducting plan. They are scheduled to start roughing in the ventilation ducts next week.

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