Major Remodel Details
I have so many questions and so little time, will try to keep it brief but doubt I will. We are in the middle of a major home reno (climate 4A) stuck with a contractor that is more concerned with getting it done than doing it right. So it’s been an adventure in babysitting for me to have to explain my position on why I want things detailed a certain way for this old dinosaur that hasn’t changed much with new technology and the application of energy-efficient building. I should have hired Travis from Catalyst but they were too busy.
Here goes…
1. We had to cantilever an 18′ long section about 20″ wide in our new primary. Before I am berated for building this way, know we had to work within the confines of the existing foundation and this is what it gave us. After air sealing and insulating this area, should it be part of the conditioned crawlspace or should I block it off with rigid foam where it intersects the foundation wall? Understand this is the area directly beneath the head of our bed so comfort is a priority. Further, the grade is super low on our property and the bottom of this is going to be barely 6″ above the ground – I plan to detail the bottom of this with 3/4″ PVC or MiraTec solid sheets, then wrap the bottom of the plywood wall sheathing with flashing tape and a piece of metal or plastic rigid flashing, finally putting landscape rocks below it instead of organic material. Anything I’m overlooking / not thinking about with this? It keeps me up at night.
2. The HVAC guys took the path of least resistance. They used cheap 4″ flex duct for 3 exhaust fans in an unconditioned attic. Plus when we moved our return air and one supply run, they just kept the supply duct running through the return air bay and spray foamed around it. Are both of those worth fighting with my contractor to change? What is the real risk of condensation pulling through those flex exhaust ducts and creating a mold risk with cellulose? They also pointed the exhaust fan termination vents back at the house – I assume to keep the wind from blowing in, but I’m going to install the Panasonic soffit termination vents instead.
3. I want to air seal drywall as much as possible to stop communication between walls and attic space. If I staple a 6″ piece of sill seal on the face of top plate, and wrap it 90 degrees and staple that to underside of the joists – will that be enough? What else can I add now that we are totally dried in?
4. Is it worth caulking all the stacked up studs around windows? Is this a potential spot for air leakage? It seems like overkill but is easy enough to do while exposed.
5. I caulked and taped the outside of the sheathing to the top of the foundation and the WRB will lap over that. I followed this same process on the interior and caulked and taped bottom plate to subfloor (side note: SIGA is amazing). One weak point I still need to address is the top of foundation to sill plate from inside, just haven’t had a chance to get down there yet. Any other easy access points to address before siding goes on?
6. The sheetrock is down in our unconditioned garage so I have access to the full wall. I’m thinking of throwing on a piece of 1.5″ unfaced EPS on the common walls from the top of stem wall to bottom of existing ceiling. Any vapor or condensation concerns with that? On the interior side will be fiberglass batt insulation touching the foam board – should this be unfaced? Also there is no way to partition off the attic over garage as it breathes using gabled and a ridge vent – knowing this is it worth blowing cellulose into garage?
Any commentary or additional info is welcome. I’m trying to stay as ahead of the subs as I can – seems to be fairly easy when no one is on site for weeks at a time…
Michael
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Replies
Michael,
I'll take a stab at a few:
1. Definitely air-seal between the cantilever and the rest of the house. The is no way to make those joist spaces "part of the conditioned crawlspace". That floor will feel cold unless you add a layer of rigid foam to the underside of the cantilevered joists. You also need to add sealed rigid foam to the inside of each bay at the rim-joist before filling the bays with batt insulation.
2. The first part - whether it's worth fighting over - I'm not sure.
Instead of the Panasonic, I would use a directional soffit termination which directs air away from the house, and locate it close to the eave. Something like this: https://www.dkhardware.com/national-brand-alternative-sdv4wxzw-4-ft-soffit-dryer-vent-white-product-3928058.html?utm_source=google&utm_medium=shopping&utm_campaign=free_listings&gclid=EAIaIQobChMI_rvE8N-lgQMVoRKtBh1J1wxeEAsYBSABEgJriPD_BwE
3. The folded sill-seal works remarkably well.
4. I don't see much point. It sounds like you are using the drywall as part of your air-sealing strategy. Make sure you seal wherever it terminates (at the floor, and framed openings, wherever it meets another material).
5. Sounds good.
6. Treat the garage wall like any other exterior one. If you are adding foam, stick to the advice in this blog: https://www.greenbuildingadvisor.com/article/calculating-the-minimum-thickness-of-rigid-foam-sheathing
Thanks Malcom - always appreciate your insights and your activity on here - you are an avid responder which is fantastic and appreciated by all us noobs. :)
1. "That floor will feel cold unless you add a layer of rigid foam to the underside of the cantilevered joists." The framers ran the sheathing below the bottom of the exposed joists about 2", so I had just enough to tack on 1.5" of rigid foam and seal the entire perimeter of the underside of the floor system - creating at least some thermal break between the outside and the wood. I have already done 2" of rigid on the outward rim joist too and just need to seal it all up. I suppose I was thinking if I got enough foam on the outer rim joist and the bottom of the cantilever, I could leave it open to the conditioned interior crawlspace, but sounds like I'm better off getting as much insulation in there as possible and "extricating" it from any conditioned spaces.
2. These are the Panasonic vents, you can actually direct the air away using these as the louvres are adjustable.
https://na.panasonic.com/us/home-and-building-solutions/ventilation-indoor-air-quality/ventilation-accessories/ezsoffit-venttm-soffit-termination-system
4. "Make sure you seal wherever it terminates (at the floor, and framed openings, wherever it meets another material)." Good advice, I probably wouldn't have thought to do it around an interior cased opening, but can see why it needs to be there too.
Thanks again - I'm always amazed at this community's willingness to take time to share or write a response!
Michael,
And as my response illustrates, sometimes the advice isn't all that useful.
1. I've got my rim-joists mixed up. If you are blocking and sealing at the foundation, you don't need to use foam between the joists on the cantilever. However if it's there all the better. Here is a good (if a bit complex) section: https://www.greenbuildingadvisor.com/article/positioning-control-layers-in-a-cantilevered-floor
2. I didn't know the Panasonic vents were directional. Thanks!
I am adding to this a question about air sealing I realized upon working last night. I suppose I also need to figure out a way to capture all the outlets, can lights (another sore spot), and holes drilled in plates where wires come down, don't I? Do I need to figure out a way to box in all the outlets with foam so I can gasket the face of it? Or, since I've got gaskets on the top and bottom plate, do I not need to worry about those outlets since they're "in the sealed zone?"
Thanks
EDIT: I just ordered some box shells so will use those to seal up my j-boxes. Whew, there are a LOT!