Rumson, NJ, US
Pete is a consulting engineer and building inspector by trade. At various other times in his life, he's been a rocket scientist, vineyard manager, winery consultant, musician, sailor and furniture maker. He's built or renovated is share of houses over the years, and currently resides in an 1890's house that he's renovated for energy efficiency. He's moving to Vermont soon, where he hopes to take up distilling as a new direction. He hangs out at GBA to learn more from the experts before designing and building his next forever home.
It's more likely condensation than wicking. The hints are in your posted observations. It happens when there is rain and it is humid, even (or especially) in winter. In winter in MA, it gets cold and the floor of an unheated garage gets cold, too. If the weather warms up outside and it rains, then you are going to have dewpoints above freezing and a slab temperature near freezing. Air leaking into the garage condenses on the slab. In summer, ground temperatures are lower than the outside dewpoint, and this also points to condensation issues. The tire tracks are attracting extra moisture because of the road salt that is soaked into the floor. Salt is hygroscopic and it attracts moisture, accelerating the time it takes to saturate the surface. The pattern starts at the garage doors because the cold air is colder there and the warm and humid air is warmer and more humid - the closer you are to the doors, the closer conditions are to outside conditions. Unfortunately, there's not much to be done about it. Improving the weatherseals on the garage doors or replacing the door with an insulated and sealed door can help by keeping outside air out of the garage. This will limit chilling in cold weather and also limit the ingress of humidity with warm and humid air. Heating the garage in winter would help, but at a big energy penalty. Dehumidification in summer would also help, again with an energy cost. I dehumidify my detached garage in summer just to keep my lumber in good enough condition to use for furniture.
Posted: 05:05 pm on October 15th 2018
I think I get a part of what bugs him, and it bugs me too. Here we've gone and made houses that are tight enough and insulated well enough that we can dispense with all of that expensive, space-consuming and leaky ductwork, and just heat and cool our houses with minisplits. But then we realize that we made our houses so tight that they need ventilation, and to do that, we have to introduce a whole new set of (usually poorly designed) ductwork. The whole HRV/ERV thing really is a kluge, and someday, some smart person is going to figure out a better solution. I don't think T. has the right solution, but at least he's thinking outside the box.
Posted: 07:15 am on October 16th 2018
From what you describe, I would bet that the HVAC system is bleeding heat into the attic. Most HVAC ductwork is incredibly leaky, despite the insulation. A duct blaster test is similar to a blower door, but just for the ductwork. Ask your Mass Saves assessors if they do that testing. Once the ductwork is sealed, take a look at burying it in insulation. A blower door test can also tell you whether the duct boots are well sealed to the ceiling. That's another big area for heat loss to the attic. Pressurizing/depressurizing with a blower door and using an IR camera from the second floor and the attic is another great way to find heat leaks.
Posted: 12:36 pm on October 17th 2018
Why not just ignore the 2" foam on the roof deck and put a foot of cellulose on the 2x6 rafter ceiling, leaving the attic vented? Cheap and easy, and you don't have to worry about the vents, cantilevered rafter details and all of that complexity.
Posted: 12:57 pm on October 18th 2018
You're already halfway to an EIFS finish, why not consider that? Change the exterior polyiso to EPS and use fiberglass mesh and finish. This way, you can keep the Arts & Crafts styling for the most part. 4" of exterior is the maximum EPS thickness for fire code reasons, but that's still better than nothing right now. A FAWRB is certainly more expensive, but I think it's going to make your life much easier. If you use grooved foam, you can use adhesive basecoat to apply it to the WRB. No fasteners involved in the entire finish system. Waterproofing the windows becomes simple. The WRB is also your air barrier, though the EIFS skin is an excellent second air barrier. As long as you provide a good drainage break between the above grade walls and the foundation, this is pretty much a bulletproof system. This is a commercial EIFS and you want to find a contractor with primarily commercial EIFS experience. You will have a much better chance of getting the job done right. The only real downside is termites. They can still get into the below grade brick and come up through the walls. How is the termite pressure in your area? If anything more than "none", you should talk to a bug company about soil pretreatment or bait/monitoring systems.
Posted: 07:39 am on October 19th 2018
In addition to a case or two of caulk, you should invest in a commercial grade foam-in-a-can system and gun. Hilti makes a pretty good one. You will save money over buying lots of cans of Great stuff, and get a better job, too. A god rule of thumb is that joints less than 1/4" should be caulked, but wider than that should be foamed. Like Martin said, this approach takes a long time and success is not guaranteed. If you do it yourself very carefully, it can be done.
Posted: 07:43 am on October 19th 2018
It is important to read the manufacturer's instructions very carefully. make sure that it it rated for exposed use specifically in attics, and specifically attics that are used for storage, if yours is one of these. Reading these specs can be very confusion. You can have several different grades of foam on one spec. You can have foam that is listed for one type of protection inside walls and other building cavities, a different type of protection in attics used only for access to equipment, and yet another one for storage attics. And then there are all the options for crawl spaces. If your foam is actually rated properly for exposed use in the area you will use it, then go right ahead. If you are just concerned and want to reduce the risk, adding a ignition barrier will reduce the risk of fire. A thermal barrier will reduce it further. There is never a prohibition on going above code.
Posted: 02:27 pm on October 19th 2018
I would never even consider a ventless fireplace in a super tight house. Ventless is really bad even in a leaky house. There is no way that a HRV/ERV system could deal with all of the combustion products produced. You would just be asking for serious health risks. I don't have any specific products in mind, but others on this list might. From my experience with these units in general, I think the firebox and vent are going to either be pretty well air sealed or pretty easy to seal. The difficult part might be the thimble through the wall. These are concentric sheet metal cutouts, with air spaces on purpose so that heat is not conducted to the building framing. You're generally not allowed to use spray foam or anything else to fill the gaps, and that will make it very hard to air-seal.
Posted: 02:33 pm on October 19th 2018
The advantage of over ventilating with the ERV is that you also wash out the VOCs that are still outgassing from all of the new stuff in the house - cabinetry, finishes, carpets, furniture, etc. Steve does mention that he has an ERV. That's not going to dehumidify as effectively as an HRV, because it's capturing the outgoing humidity and transferring it to the incoming airstream. During the swing seasons when the outside DP is low and the temperatures not too low, opening the windows is going to dehumidify much more effectively than the ERV. With outdoor temperatures in the 10C-20C range, open windows are probably the most efficient and effective ventilation and dehumidification. Adjust the windows to be open just enough that you don't have to add much heat and let the indoor RH float for a few weeks. Of course in the great white north its probably already too late for that. I'm still enjoying the no heat - no cooling season in zone 4.
Posted: 01:08 pm on October 18th 2018
The HVAC system doesn't create new oxygen or bring it into the house. That is unless it is hooked into an outside air system. Most HVAC systems just circulate what you've already got, good or bad.
Posted: 05:08 pm on October 15th 2018