Humidify via forced air system?
Zone 4a, 5500 HDD 65.
A customer of mine called about seasonal gapping of their 3/4 x 2-1/4 white oak floors. We’ve had some below-freezing weather lately and I’ve been boiling my teakettle periodically to combat it in my house. I took a look and the gapping is more than I would want myself. They have a forced air heating system with a heat pump and strip heat backup, so one option is to install a humidifier at the air handler. The air handler and about half of the ductwork is in a vented crawl space. The house is two story, and the wood flooring is upstairs in the main living area. There are a couple of carpeted bedrooms downstairs that are not used much, and the registers are closed in those rooms. The humidifiers I have seen are steam units with electrical and plumbing connections and probably make for a fairly expensive installation.
Any comments on systems like these? Are they reliable and effective? I will probably ask the owners to run a portable unit for a while and see what changes, but they have an ultra-spartan house and a humidifier sitting there for long is going to be unwelcome.
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Replies
David,
I'm not a fan of humidifiers, which can cause more problems than they solve.
A home that is too dry in winter is almost always a leaky home. (It's the high rate of air exchange that's the problem -- too much infiltrating dry outdoor air.)
The best solution is air sealing. The best air sealing job is usually done with a blower door guiding the sealing work.
I would start by sealing, insulating and conditioning the crawlspace as well as sealing all ductwork. It's possible that leaky ducts are contributing to the pressure imbalance that is driving infiltration, but almost certain that the open crawlspace is the intake "port" for most of the infiltrating air.
Of course, seal the upper ceiling as well.
A little more background on the house. I have tested it and air leakage is just under 7 ACHn. I got part way thru duct blasting but ran into a couple of issues and did not get a conclusive test re leakage to the exterior. I can return and finish testing when the owners hit the road, but they've been around for a few months and I hesitate to do this stuff with people trying to use the house.
The upstairs ceiling is mostly high and it's 2x6 T&G with batts and venting above, so it's not a real air barrier, and that's where I think most of the air leakage is occurring. Fixing it from above would be a massive undertaking, and fixing it from below would probably mean trying to caulk all those V-grooves without making it fugly. It may be that what I need to do is find a wood-tone caulk with low sheen and try to stealthily seal the lid from inside.
I know that you are both right about dry exterior air as the problem, but for now I'd like to set aside the air-sealing angle. We have 2-3 months a year where dry conditions happen, and if there's a way to bump the interior RH a bit during those times and solve this problem, it may be more palatable to the owner. I am currently collecting some info with USB dataloggers around the house, and will go retrieve them later in the week and have some numbers to look at.
Martin, I assume when you say that humidifiers can cause more problems than they solve, you're talking about excess humidity? I'm wondering about condensation inside the ducts in the crawl.
David,
The solution to the problem of the ceilings is called drywall. Later, if they can afford it, they can always put more T&G over the drywall.
The danger -- especially in a leaky house like the one you are describing -- is that running the humidifier will lead to more condensation or moisture accumulation in hidden areas of the building envelope.
If your hunch is correct -- and I don't doubt it -- that exfiltrating air is leaving the house through the ceiling boards, then moisture will easily contact the cold roof sheathing and form frost or lead to very damp roof sheathing.
A half-fast solution is no solution, particularly when it will almost certainly create more problems than it solves.
The ceiling cannot be tightened with caulk, but needs a real air barrier - either foam from above or removal and replacement as Martin suggests.
If the owners don't want to pay for a real solution, I would walk away from it.
David, brand spanking new home that I worked on all last winter after the contractor was let go. Same set up in their great room, T&G cathedral ceiling nailed to rafters with kraft faced fiberglass batts and vent chutes. In the attic there is a breeze of warm air coming up from the chutes cathedral area. On the roof, the snow melts like there is a torch below. The biggest icicles ever.
I let them know that I would have to rip redo it completely if they wanted T&G to remain. Nope. They paid way too much for the home already, it looks nice and they are done. Heat tape added for the icicles and they just pay through the nose for propane.
I can't even make sense of the situation. The cost of fixing this small error is just way too high for even myself to be for.
In my case, I was starting at $10,000 and realistically headed toward twice that. The area involved has two huge valleys and overall is a very large space. Not a pretty picture.
Caulking was my least expensive temporary fix idea. I was going to use Sikaflex. I have used it before by the box to build kit log homes which leak notoriously between logs, and in corners as they get a few years old and shrink down but not evenly, hanging up on fasteners an whatever.
Green? No. Nothing green about this particular home. Or Sikaflex. The expensive fix did include cellulose, taking down ceiling and reusing as much as survived the rip out.