Drolet OAK and humidity problems

I have a Drolet Escape 1400 which I installed this winter and have been thoroughly enjoying. The problem is the humidity in my house has dramatically dropped.

I'm looking into the outside air kit as part of a solution to this, but oddly enough on this insert this wouldn't be a sealed connection between the combustion chamber of the insert and the outside air. There is still a pathway from the household air to the combustion chamber via the pathway for the blower circulation. This makes it seem like a nice gapping hole between my house and the outside with nothing more then some plastic shutters on the outside air intake.Why do they design it this way? Is it normal? How do other people deal with low humidity and inserts, considering you can't do the kettle of water trick like a on a stove?

Humidity will improve some with an OAK, but you will likely still need to humidify some. The PE summit has the same problem of a outside/inside breach when Oak installed except no plastic shutter only holes; consider tabling it (US version) or start plugging the holes/modifying. We use a small separate humidifier.

I was thinking that we would have the same problem in our house this winter and had planned on buying a whole house humidifer (big enough for our place anyways): http://www.sears.ca/product/kenmore-md-454l-digital-humidifier/642-000017871-758_3_29982OC

I've also found that drying all our laundry on racks around the stove makes a fair difference in humidity. It's better this year with the stove than it was last year without (electric heat).

The best solution is to buy a one, or more depending on the size of the house, stand aloe humidifiers. Personally I prefer having several smaller units rather than one large one.

First question is what do you call dramatic? Second question is why do you think that is a problem? It is common misconception that stoves "dry out" the air. Stove heated homes are typically far warmer than others, which decreases the Relative Humidity, but does not decrease the quantity of water held in that air, and does not change the dewpoint. The quantity of air used by a properly running stove is apparently not significant in the overall air leakage of the typical home, so using an OAK probably won't do much to retain humidity.

If you are trying to protect valuable furniture or items from low %RH, then a humidifier may be a good idea, but it could increase the dewpoint to where you cause condensation, and any health benefits of higher humidity could be outweighed by increased mold growth. Don't spend a lot of time fixing a problem that may not exist.

TE

I'm seeing cracks in furniture and wood floors, trim and molding starting the shrink and expose the caulked joints, stuff that wasn't hapening last year without the fireplace. This years has been colder which is also probably a contributing factor. I'm going to try and borrow a hygrometer from the piano tuners I work with and get some real data to compare to.

a basic humidifier is around 50 bucks...

Perhaps one of the larger console style humidifiers in the same room as the stove? I have a little kettle on top of mine, but that isn't really enough to keep up with humidity in the house. From what I remember last year, because of the milder winter the humidity didn't drop off as much and some of the dryness might just be from the recent cold snap.

That being said, I bet a larger humidifier or a few smaller ones would take care of the issue. Since it's been so dry I've actually kept a humidifier running in the bedrooms at night, during the day we kind of like the dryness and just don't want to wake up with a dry throat. Larger console humidifiers might cost a little more, but I'm sure that would help out with the problem and they just roll into place and plug in.

FWIW - my basement dehumidifier in town (sitting idle) shows @ 35% through the recent cold snap, down from @70% in the summer months (when it runs steady). It is very dry this winter, I think even a bit more than usual. Crawl space dehumidifier at camp hasn't run at all for a couple weeks. All my window and baseboard trim work has tiny lines at the mitred joints. The summer will fix that. This is a crazy winter for temp and RH levels / swings.

I suggest a sufficiently large humidifier with automatic controls as humidity requirements will vary daily. A house with large air leaks require more humidification. Don't get one too big or too small.

Here is an example of the suggested humidity levels:
Outside Temperature Indoor Relative Humidity
Above 50 °F Not over 50%
Above 20 °F Not over 40%
Between 10º & 20ºF Not over 35%
Between 0º & 10ºF Not over 30%
Between -10º & 0ºF Not over 25%
Between -20º & --10ºF Not over 20%
-20ºF or below Not over 15%

The better the vapor barrier,windows, and insulation on the house, the higher humidity levels you can run. The above is for the average house.

One problem with those guidelines is that they are assuming a room temperature somewhere about 70F. With wood heat, temperatures are often more like 80F, and 40% RH at 80F has a dewpoint of almost 55F.

TE

This EPA document on wood combustion indicates that theoretically ideal combustion requires about 6.4 pounds of air per pound of wood, and in practice it actually requires 50-100% more air than that because real stoves aren't perfect. So, taking a hypothetical 30# load of firewood at 20% dry basis MC, meaning there's actually 25 pounds of wood after discounting the water content, ideal combustion would require 160 pounds of air. Add 75% to make it more realistic and we're at 280 pounds of air. At 80F the specific weight of air is 0.07353 lbs/cubic foot, so we're looking at 3808 cubic feet of air to burn that load of wood. If it's a 6-hour burn, that's about 10.6 cfm of air being consumed and replaced with outside air.

To put that in context, this site suggests that it takes at least 0.3 air changes per hour for decent indoor air quality, and this page says that a typical tight, newly constructed home might be around 0.6 air changes per hour, and a leaky older house could see up to 8 changes per hour. If our hypothetical house is 1500 square feet with 8' ceilings, then the bare minimum rate of air exchange is 60 CFM.

I don't know how realistic my assumptions are (30# load of wood to heat a 1500 sq ft house for 6 hours) but if they're even close then it does seem that an outside air intake can only hope to make a marginal improvement.

Jon, thanks for putting numbers on it. I had previously proposed that a stove might theoretically "dry out" air by drawing more dry outside air into the home and someone had given similarly low values for air consumption to yours.
Adding to those assumptions, you can also assume that if an OAK was not needed to achieve draft, the house is nowhere near the 0.6 end of that scale.

TE