To recap: Last post I started reviewing possibly the worst house I ever audited. The house had built in 2008, which hit one of my pet peeves: That new automatically means good. But to reiterate a buddy’s favorite saying, “a house built to code is the worst house you’re legally allowed to build.”
An aside: A comment on the previous post mentioned that the building code covered a good deal of these issues years ago. I have to admit, I was being broadly harsh toward the building code when I had air leakage standards and thermal bypasses more specifically in mind. For example, Maine hasn’t adopted a statewide energy code as part of the building code. Both IECC 2009 and 2012 include air leakage standards, the testing of which would’ve revealed many of these issues.
The building: It was a 2008 ranch built into a hillside. It had an attached garage with a centrally located chimney, framed in between the garage and main house. An open concept kitchen was just off a cathedral ceiling great room that occupied a large chunk of the first floor plan. The master bedroom was over the garage. It was nice.
The Solutions
Moisture – One of the biggest challenges was tightening a building envelope with so much moisture. It’s a very bad sign when a house with a 6200 CFM50 blower door reading, flying through 1200-1500 gallons of oil each year is having mold problems.
Loads of energy pumped into a building enclosure and more air flow usually means more drying. If we just air sealed without any provisions for reducing moisture levels, the mold could potentially explode. It helps not at all to fix one problem and create another. This meant reducing moisture was the first priority.
Improving the exterior water management was tackled first (AKA getting rid of the pond in his front yard). Rainwater and snow melt was overwhelming the foundation’s existing footing drain so it needed some help. The plan was to do the exterior work first, give it a couple months and track the interior humidity levels. If they came down, great. If not, we may include some more interior moisture management.
The homeowner was fully committed to fixing all the existing problems so out came the back hoe. The contractor hired for the external water mitigation trenched down to the footer drain. We were pleasantly surprised to find the footer drain nicely wrapped in a drainage screen and relatively clear of muck and blockage. It was functioning; just being overwhelmed by the hill drainage’s massive water volume pressure.
The entire sub-grade hillside section of the foundation was coated with two layers of UGL Drylok. This concrete sealant is waterproof and vapor semi-impermeable, providing much more protection against infiltration that the bitumen damp-proofing.
Once the trench was filled back in, we landscaped the hillside ground, creating an aggressive drainage slope. About eight feet out from the house, leaving space for some landscaping later, we added a topside french drain. A 24″ trench was dug across, laid a perforated 4″ pipe at the bottom wrapped in drainage screen and filled with 1″ crushed gravel fill. Luckily, the hill provided a natural gravity drain out the sides.
Next was sealing the interior concrete. Normally, sealing concrete in high moisture situations may lead to upward capillary movement of the water. Not a worry here as the pressure treated sill plate was installed with a sill seal capillary break. The foundation floors were coated with 2 layers of Drylok. We left the walls alone, as we’d be applying closed cell spray foam later, itself a vapor barrier.
Next was evaluating the improvements. We left several humidistats throughout the basement and house and the homeowner checked them regularly, recording the relative humidity. Once we had a several weeks of data showing the humidity and moisture had come down (no more window condensation) we moved on to insulation and weatherization.
Time would prove that an extra step like adding an interior perimeter drain was not necessary.
Ventilation – Because we would be tightening the envelope up a great deal, we made provisions for combustion air for the heating system and a heat exchange ventilation system. One might not think that this house with its extreme air leakage would need mechanical ventilation. But we would be doing a lot of air sealing and more importantly would be sealing the entire ceiling, cutting off any stack effect driven air flow. Adding mechanical ventilation set to ASHRAE air flow standards made the most sense.
Air Sealing & Insulation – The Attic – One stroke of luck was that the cathedral ceiling was constructed of scissor trusses with enough space to work behind. This allowed easy access to the back of tongue and groove finish, the open chimney framing, the unsealed soffit vents, the recessed light canisters. All good news.
The existing fiberglass batts (two layers of crossed unfaced 9″ fiberglass batts) were pulled aside carefully. It was in good shape so would be retained and replaced.
The recessed lights were encapsulated with drywall boxes and caulked. The open chimney frames was covered with light gauge aluminum and sealed with high temperature caulk. The soffit vents were sealed with solid foam blocks flush against the exterior wall’s top plate and the existing foam proper vents. The top of the marriage wall between the garage and main house was sealed. Finally, 2 inches of closed cell spray foam was applied to the attic side of the cathedral ceiling and once cured, the fiberglass was replaced. After all the air sealing and insulation work completed, the blower door test out was 1925 CFM50. Not ridiculous tight but less than a third the initial reading.
Air Sealing & Insulation – The Basement – The basement/garage was next. I’ve never been a fan of defining the thermal enclosure at the garage door. The garage door is too difficult to insulate and air seal satisfactorily. The garage occupied the left hand third of the basement, under the master bedroom. A problem I forgot to mention last time was that the garage was plenty cold and the interior garage framing walls were open over their tops, with only cripple studs attached to the joists.
We pulled down a one foot strip of drywall and pulled out the fiberglass. I know we saved the fiberglass before but the garage ceiling was more problematic. From the exterior, the soffit vents on the cosmetic eave was blocked with foam blocking and sealed. The open space over the interior frame walls were blocked and sealed. Insulweb was tacked in over the gap in the drywall and densepacked in cellulose. We patched and mudded the drywall and all the cracks and penetrations were sealed with foam sealant and caulk.
Lastly, all the basement walls were sprayed with 2 inch closed cell foam and tumescent fire retardant paint.
Heating System – Not too much here. The single zone was woefully short in supplying heat uniformly. Rather than re-zone, we decided to see how the house would work after the weatherization effort. The homeowner added 2 inch closed cell foam pipe insulation to the entire hot water loop and other hot water pipes.
Problems Solved?
We checked back in periodically over the next couple years. The husband has been closely tracking the energy data or had been as of about a year ago. The heating bills were around 40% of their previous levels and the moisture issues have largely disappeared.
In the interim, the folks had gone ahead and re-zoned the heating system into three zones and added an outdoor reset. It was mostly happily ever after except for all the work need to arrive at that point.
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