Archive for the 'Air sealing' Category

Radon test results

We ordered a radon test kit from the New York State Department of Health last month. The kit is small canister of charcoal that you open and place in the test area for several days. We let it sit for 4 days in our basement, then sent it off to the testing lab. The results came back about a week later.

For reference, the EPA defines the safe limit of radon gas at less than 4 picocuries per liter of air (pCi/L). Our result was 38.6 pCi/L, almost 10 times the limit, ouch!

We had been somewhat slow to get the basement tested for radon because we spent a great deal of time and care sealing everything in the basement. Our blower door test confirmed that we had done a good job overall. So we assumed we would have no problems with radon.

Unfortunately, the radon is getting in, and because the house is so tight, it’s not getting back out.

Thankfully, we installed vent piping under the slab and sub-slab insulation when we built the house. We capped it off at the surface hoping we wouldn’t have to use it.

How sub-slab radon mitigation systems work

A vent pipe installed below the slab and vented to the outside depressurizes the area below the slab. Radon gas will take the easiest route to the outside.  Our vent pipe runs the full perimeter of the inside of the footing under both the slab and 6″ of XPS insulation (R-30).

The EPA recommends running the vent pipe up the center of the house to the outside because the warmth of the house creates a stack effect, inducing a natural draft in the pipe without using mechanical ventilation. Unfortunately this method also cools the house in the winter, something we hoped to avoid.

So rather than run the vent through the house, we ran our exit vent pipe through the footing to the outside of the foundation wall and capped it at surface level. We figured if/when we determined we had a radon problem, we would extend the vent pipe up outside the house, through the soffit, into the attic, connect to an inline fan and exit through the roof.

The fan will use energy continuously but at least it won’t be cooling the house in the process. The installation cost will be minimal since we did most of the hard work when we poured the foundation.

In hindsight, we should have found a way to integrate the vent into an outer wall where it could still be insulated from the interior space. Running the vent up the outside of the house will take some work to make it not look like a strange pipe on the side of the house. We’re going to try to disguise it as a gutter. We’ll have more info on the details and photos as we start work next month.

For more information on radon in the home, read this EPA guide, A Citizen’s Guide to Radon.

Photo Tour

We’ve been living in the house for one month and are now mostly unpacked (except for Larry’s office) so I thought it was time to give everyone the 5 cent tour.

Still some work to do: Once the basement is cleared of construction tools and supplies, we’re going to start setting up the root cellar, work tables, homebrew kit & dart board (a.k.a. man cave.) We’re also still debating the best way to hang artwork on the walls. Larry’s hesitant to put nail holes in the exterior walls he worked so hard to air seal. And we still have a lot of stuff in storage that we need to unpack, but for now we’re just taking a few weeks to enjoy the place. We love it!

Last update of 2011

Lot’s of news this week. We got our Certificate of Occupancy (C.O.) on Wednesday! We can officially occupy our home this weekend.

We worked like crazy last week and over Christmas to finish all the odds and ends for the final inspections. We finished all the electrical Wednesday, 12/21, and had the final electrical inspection the Friday before Christmas. Our water test results arrived Christmas Eve. We spent the rest of Christmas weekend finishing up the porch railings and temporary stairs for the final inspection on Tuesday, 12/27. Our inspector gave us the thumbs up and faxed us the C.O. on Wednesday.

But wait, there’s more… Our contractor Warren entered the Energy Star program with our house. In order to complete the program and qualify under the 2011 rules, we had to get our final inspection and blower door test before the end of the year. This happened Thursday, two days before the end of the year. Final blower door result was 131 cfm, an improvement of 28 cfm from the shell test we did back in September. We’ll post more information on the Energy Star process next month when things settle down. It’s the only certification we’ve chosen to do for the house.

Our kitchen counter tops also arrived yesterday and were installed. The counters are Cambria Quartz (color: White Cliff.) We chose a manufactured quartz counter because we wanted something durable and low maintenance. And we chose Cambria because it’s the only American company manufacturing quartz counter tops. It looks fantastic.

And we generated our 5th megawatt Thursday. It took us almost 60 days to do it. That’s 5 megawatts for half a year. The system went online June 2nd.

We have a few finish work projects to complete. As we were running short on time, Jill found tile contractor, Chad Greenslet, out of Bennington to finish our shower tile job. He installed the Schluter and tile in 2 days, but ran out of tile. We thought we had ordered extra, but somehow miscalculated. The extra tile arrived today, so that project should get finished up next week. Jill is also working with a local glass supplier to install a frameless shower door.

The site-cut maple intended for our stairs is still drying out in our basement. At some point soon we’re going to have to decide if it will be ready in time, or if we should purchase other material for the stair.

95% of the trim is installed. The holes have to be filled and cracks caulked before it gets painted. Doors have to be painted too. Jill is hoping to get the two bedrooms finished this weekend so we can start moving some stuff into them.

Also, a few pieces of siding trim for the basement entry have been sealed and are awaiting installment.

But that is about it. We’re down to the final punch list. We have to be finished in two weeks for the mortgage appraisal. That is our other task – converting our construction loan over to a mortgage. More on that process soon as well.

Friend or Foam?

Many spray foam kits are targeted for the ‘do it yourself’ crowd, but if you do it yourself and you encounter problems, be prepared to remove bad foam.

The good news

Foam is great in spots where nothing else will work quite as well. We used foam primarily for air sealing in odd spots, but also for insulation value in areas where it was difficult to blow cellulose. See our previous post on this topic, “Foam continued…“.

The bad news

Foam can be fussy. Foam itself must be within a specified temperature range, the surface must be clean and within a specified temperature range, the hose and gun must be in perfect working order, and once you start spraying you can’t stop for more then a few seconds without gumming up the spray gun. In addition, you must provide adequate ventilation and wear protective clothing, breathing gear and goggles. Does this sound like a DIY project? I’m guessing most applications of spray foam are successful. We had used about 6 kits before we ran into problems, but sometimes things go wrong.

In our case, since we are not professional installers we were not immediately aware that something was going wrong. The foam did not appear to be expanding as usual or curing properly. It looked a little more yellow than white and felt rubbery when poked. By the time we realized something was not right, we had sprayed some 40 linear feet of band joist area in the basement. We’re still not sure what caused the problem. Was it a bum kit or bad hose and gun? We had followed all the same precautions as before, but we had very different results.

At first the manufacturer told us to just let it air out, it would cure on its own, it just might take longer than usual. So we vented and waited a month. All we had was a sticky smelly mess.

After several conversations with the manufacturer, we were faced with two options. A. Remove the bad foam. B. Spray over it with a (hopefully) good layer of foam to seal in the bad smelly stuff. We decided to remove the foam. For more background on why we chose to remove the foam, see Martin Holladay’s post on GreenBuildingAdvisor, “Spray Foam Jobs With Lingering Odor Problems“.

The ugly

Removing bad foam is a nasty job. In our case, removing foam from a roughly two foot deep cavity at the rim joist area around 12 inch deep trusses with sharp metal plates. Not an easy job. My arms ached and even though I wore a mask and ventilated the space I still woke up with headaches the next day.

When I started pulling out the foam, I realized there were several areas where the foam had shrunken away from the sheathing by as much as an inch. I’m a bit concerned about this. Was this just due to the bad foam, or had this happened in other areas?

I tried to remove as much of the bad foam as I could, but there were areas at the corners where I couldn’t reach and areas behind ducts and wires that I didn’t want to be poking around with the serrated knife I was using to cut the foam into sections for easier removal.

I was able to remove roughly 80% of the bad foam. For the remaining areas, we just foamed over them.

Mostly happy ending

So far, our re-foaming efforts have been positive. The replacement foam kit provided free by the manufacturer yielded nice expanding foam that cured normally. We’re not quite finished, but I’m keeping my fingers crossed that we won’t encounter any more problems. I’m also hoping that we don’t encounter any more smelly issues when the temperatures begin to rise next summer.

First floor sheetrock

Last week Warren and crew sheetrocked the main room on the first floor. Before they could do this, gaskets were installed along the exterior walls and furring nailed on the ceiling, same as the second floor. The main objective of the gaskets was to seal the exterior walls from air leakage originating from inside the house.

The only remaining areas to sheetrock are the two small rooms off the main space (pantry and study), the window returns and the 1st floor stair area. Hopefully Howie will begin taping later this week. We’re in a race to finish taping and painting the first floor before the wood floor and kitchen cabinets arrive in 2 weeks.

Shell blower door test results

Today was the big day. Matthew Evans from Newport Ventures came out to the house to conduct our first blower door test, and the results were very encouraging. Our final reading was 159 CFM or 0.56 ACH.

This was the first of two blower door tests. This first test is used to determine the air tightness of the house enclosure or shell. All plumbing vents and air ducts are blocked for this test. Doing this test before the house is fully insulated makes it easier to find and fix any leaks.  The second test is conducted after the house is finished and is considered the official number.

For this first test we were shooting for 200 to 300 CFM (see earlier posts, How tight is tight enough? and The cost of infiltration). Our initial testing over the weekend using a blower door our insulation installer loaned us gave us a reading in the 250 to 300 CFM range. This was helpful because it allowed us to pinpoint a few areas in the shell that we had missed, the connection of the ERV ducts to the exterior and a few other plumbing and electrical penetrations.

The initial reading from Matthew today was 185 CFM. In order to convert that value to air changes per hour (ACH) you multiply the CFM times 60 and divide by the volume of the house. He had calculated the volume of the house as 16,896 ft(32′ * 22′ * 24′). The resulting ACH is 0.66. If you use the PassivHaus definition of volume (at least the best I can understand) then the volume would be 13,697 ft3 and the ACH, 0.81. So we’re very close to one of the tightest standards for residential homes.

But there’s more.

We had covered all the plumbing vents and air ducts with plastic and tape, but Matthew found a few holes in our tape and lose plastic fittings. So he plugged the two exterior vents and we re-ran the test. The new blower door reading was 159 CFM or 0.56 ACH. (159 CFM was the average over 10 seconds. At the moment I took the photo above it was registering 158 CFM.) By PassivHaus volume standards this would be 0.7 ACH.

To put it mildly, this was better than we could have imagined.

But there’s no time to celebrate, we’re on a schedule. Tomorrow our insulator is coming back to blow more cellulose on the 2nd floor and in the attic, and we have siding to finish and more sheetrock to hang. Not to mention getting our gutter supplier to ship our order. I’m not having a good customer experience at guttersupply.com.

Air sealing the ceiling

Last week we were able to make progress on a number or fronts. One was foaming the intersection of the walls and ceiling from the attic side. As you can see in the photos above, only the areas that might leak air were foamed, including plumbing vent pipes and electrical boxes for lighting and smoke detectors.

We’re getting very close to being ready for our first blower door test.

More sheetrock: gaskets and taping

Thought I would share a few more sheetrock progress photos. The entire second floor ceiling is now sheetrocked and taped. This means we’re ready to foam the intersection of the walls with the ceiling, from the attic side. Then we just have to install the east door before we’re ready for the blower door test, sometime in the next week or two.

In the meantime I’ve been stapling gaskets to the exterior walls on the 2nd floor. Our primary air seal is at the exterior of the shell, but we’re also trying to seal the interior shell to prevent any warm moist air from circulating near the cellulose. The gaskets are important in 3 areas, ceiling, floor and at the intersections with interior walls.

Ceiling: The ceiling gasket is redundant with the foam that will be applied from the attic space. Basically, I don’t trust the foam or the gasket on their own, but I’m hoping both together will catch any spots we miss.

Bottom: The gasket at the bottom of the wall, together with the gasket under the wall that we installed during framing, keeps interior air from entering the exterior wall space at the intersection with the floor.

Intersection with interior walls: The vertical gasket at the intersection with interior walls keeps interior air from slipping into the exterior wall through the corner stud.

Problem area

The stairwell is adjacent to the north exterior wall and penetrates the floor planes to pass from the basement to the first and second floors. Following the approach described above, I should run gaskets around the exterior wall and at the ceiling and floor, but what about the truss area between the 1st and second floors?

The ceiling over the 1st floor is open all the way to the exterior sheathing, and to the exterior wall behind the stair. I think we’re going to need to block the area at the trusses, so air from the 1st floor ceiling can’t pass into the exterior wall behind the stair.

It’s little details like this that are rarely documented in most air sealing guides (because they are less typical) and easy to miss. I’ve been going back over all our details to make doubly sure we haven’t missed something silly.

Let the sheetrocking begin!

Well, at least for the 2nd floor ceiling.

Normally, you wouldn’t start the sheetrock till the walls are insulated. But in order to test how well (or poorly) we’ve sealed the house with a blower door test, we need to complete the air barrier, and that means the 2nd floor ceiling. This is the area where the air barrier transitions from the exterior of the house to the interior. It will be one of the trickiest areas to seal properly.

We installed gaskets around the top edges of the walls, but because we’re using strapping, it made it difficult to close all the gaps. So we’ve decided to use 2-part foam only around the edges where the ceiling meets the walls. This should ensure that we have all possible gaps sealed.

Lessons Learned

We used poly boxes at all exterior wall electrical box penetrations, but we totally forgot to do this at the 2nd floor ceiling. We’ll have to use a combination of tape and foam to seal light fixture electric boxes in the ceiling.

I think I’ve mentioned in an earlier post that a smarter way to air seal the top of the enclosure would have been to extend the exterior sheathing and air barrier over the ceiling joists. Then pile the roof insulation on top of the sheathing. This method has been used by Marc Rosenbaum, although the air barrier in this case was the roof.* This approach would necessitate raising the roof up a bit to ensure proper insulation levels at the eves. The extra expense of sheathing the top of the ceiling joists would have likely been offset by the extra labor and material costs spent sealing all the gaps with foam.

* http://www.southmountain.com/smclibrary/articles/2011_01_JLC.pdf

Attic access detail, the ‘cork’

I started working on the details for our attic hatchway a few months ago. The internet is fairly void of super-insulated air-tight attic hatchways. I found this curious considering all the net zero and Passivhaus work going on to date.

The problem is how to insulate and air seal the attic access to the same standards as the rest of the ceiling. Our ceiling will be insulated with 24 inches of loose cellulose (R-75), so I wanted to make sure the hatchway was at least equal in R value and air tight. The trick was to find a way to achieve this and still be able to open and close the hatchway with relative ease.

Our solution is nicknamed the ‘cork’. Essentially it’s a 24″ deep hatchway filled with 2 insulated components. The first component is air sealed to the interior drywall. It is a piece of plywood screwed to the ceiling within a gasket and 8″ of left over rigid insulation (R-40) glued to the top of it. This is a fairly standard approach to sealing the attic hatch. The second component (the cork) is 14″ of rigid insulation (approx. R-70) held in place by a hinged top plate.

To gain access to the attic we will first remove the lower panel from inside the house, then we pop the top barrier out into the attic. To close the access we reverse the process.

The total insulated value is R-110, but that is misleading. Due to inefficiencies of sealing the insulation to the hatchway, air can circulate inside the hatchway in tiny gaps at the edges and between the two insulated components, so I just tried to cram as much insulation as possible into the hatchway as tightly as possible but still be able to pop the cork to gain access to the attic. Only an inferred camera will tell if my efforts have been successful.

I hope this is helpful to others out there building super insulated houses with attic access from the inside. If you have a simpler detail, please don’t tell me. I feel silly enough spending 2 days building the cork. But please do post your solution to make it easier for the next person.

One last word, the code requires attics be accessible, but I don’t believe it specifies whether it has to be from the inside or outside of the house. Assuming you have an attic that needs access and your local code allows outside access, I would recommend exterior access based on my experience building a super-insulated air-tight attic access hatchway. Interior access can be done, but it’s a lot of tedious work.


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