I'm building a new home for myself in Connecticut that has radiant heat throughout using QuikTrak, with the tubing located in pre-routered panels, and directly under any finished floor.

After speaking with a knowledgeable builder in my area whom I consult with periodically when I'm stumped, I'm concerned that the wood floor I'll install (not pre-finished) and the wood trim in the house will shrink and gap over time unless I add humidification.

I do have ducts in the house for A/C in the summer, but he felt this delivery method would not work best, and suggested I look into some units that deliver steam humidification, in order keep the humidity in the 40-45% range.

Any advice, experience would be appreciated.

Regards,

Jeff
Mystic, CT

If the house is sufficiently air-tight you will likely need mechanical ventilation to get the relative humidity UNDER 40%! My place (in central MA) isn't exactly the tightest, but getting tighter, and as-monitored with meters in a 5 separate places in the house, one hasn't dropped below 43% all winter, the lowest one made it down to 30% when it was -5F outside, the rest have stayed in the mid-high 30s. After I insulate and seal the remaining attic spaces next summer I expect to need a heat-recovery ventilator (HRV) to keep the indoor humidity in a reasonable range.

But as to the flooring, the rule of thumb is if the floor temp stays below 85F there shouldn't be much to worry about. I violate that in my house by several degrees a 2" t&g birch floor for most of the winter (even before the house got tighter when we'd see 15-20% RH during cold-snaps) without much gapping (and no cupping.)

Best advice- build the house tight- it'll save energy, even if you have to buy more electricity to dehumidify & ventilate it at some point. Start with the obvious (foam sealing & insulating the foundation sill & rim joist, only use tightly sealing fireplace dampers, eliminate mail slots, foam seal all utility penetrations, etc.), then at the appropriate point in the construction, hire somebody to do a blower-door test to find the other 50% of leakage that is less obvious and FIX it while it's still open enough to do easily. Paying for leak testing & air-sealing is one of the most cost-effective efficiency measures that can be done to most houses. Worst case, you end up then buying an HRV (may be able to integrate it into your air-conditioning ducting) to help DE-humidify in winter, and guarantee good indoor air-quality without blowing heating-money out the window.

If the air-handler for the AC isn't yet fully specified, getting one with a separate heating coil to run off the boiler gives you the option of applying a little heat to the air while distrbuting the incoming ventilation air, taking the chill off it. (Air much below 100F can feel chilly right out of the vent.) The HRV won't need to run 24/7- typically a handful of minutes per hour is sufficient (depends on the design, volume of the house, capacity of the HRV, etc.) In standalone HRV installations they tend to run fairly narrow ducting to all of the rooms, but larger AC ducting can be used as well.

Speaking of AC ducts: In CA in new construction they're now required to be tested for leakage and brought under some minimum in order to meet code. It's not a bad idea in CT either, eh? (It's not as if we pay LESS for energy here in New England!)

Humidifying the air should never be a necessity in New England's climate if the house is reasonably tight. Hopefully yours will be "tight 'nuff" without much retro-hacking to make it so.

Dana,

Background -- the house is fairly far along in the construction process, it's being sheetrocked now. It's an ICF house, and very tight, and I did do a duct blaster test that showed almost no leakage, and have sealed the house with closed cell foam insulation. Additionally, I have installed separate ducts for an HRV on both floors of the house.

I want to make sure I have enough humidity, not too little. So I guess I'm trying to figure out what, if any, additional steam humidification I may need to keep the humidity in the 40-45% range.

Jeff

If you follow other blogs here, you will find that humidification is not the problem. Your HRV, a shower and pot of pasta a day should work fine. Conventional 'older' home suffer swings in humidity from 10 to 100% and wood floors move.

I spec. engineered hardwood and floating floors when possible for radiant floor heating. More stable in all conditions. Bamboo (grass really) is an excellent GREEN choice also.

MA,

So I have an HRV, how does it help increase the relative humidity in the winter?

Jeff

In structures with a very tight envelope (most SIPS) too little humidity is rare. If you radiate the floors you will have less infiltration and thus more humidity trapped in the space. Your HRV or ERV will take care of this common problem if designed, installed and operated properly. Note my smart friend dana's comments above.

As both Dana and BB both stated you will not need to add humidity to your home in the winter, you will need to remove it.

My understanding is that I want the relative humidity to be in the range of 40-45%, for personal comfort, and for decreasing gapping in trim and wood flooring. I am about to finish the sheetrock taping and mud phase, and begin painting. The radiant heat has been on for 3 weeks. I just bought an high quality moisture meter, and when I measured the level today, it was 29%. I have not yet run the HRV, so it does seem that I need to increase the humidity, right??

No, you're not living it yet. Note the comment above about cooking, showers, etc. And, don't run the HRV or your heating system until AFTER all the sheetrock work is finished. Hold off as long as possible. There will be a lot of dust generated by the remaining construction activities, dust you don't want in your heating system. My HVAC nephew said it's incredible the lengths sheetrock crews will go to fire up the furnace, but don't let them do it. Install temporary heaters.

What he said!  If it's 60-65F and 29% RH in an unoccupied space when it's been below freezing outside most of the week,  it'll stay 50%+ RH most of the winter with warm bodies exhaling, bathing & cooking, unless you run your HRV at a high enough duty cycle to keep the humidity DOWN.  Controlling the HRV with a humidistat to ventilate whenever the humidity gets over 45% will be more than enough ventilation for occupancy during the winter.  In summer you'll likely need to run the AC to keep the humidity down, since the HRV won't wring much of the summer air humidity out. (ERVs will to some extent, which is why they're highly recommended in the swampy south in air-conditioning dominated climate zones. Some even recommend ERVs as far north as NJ.)

Running the HRV at a high duty cycle in winter will be somewhat drying, but I'd be shocked if at the recommended minimum duty cycle you ever got below 30% RH.  And even if it did, it's not going to be a problem for hardwood flooring unless it was WAY below 30% and stayed very low for days or weeks, which probably takes a sustained cold snap where it stays below 10F outside.  In coastal CT this won't happen very often.  (BTW: The RH in my somewhat tighened home was in the  30-35% range this AM, when it was 9F outside.  In my not-so-tight office it was 16% RH inside at about 15F outside with similar ~69F indoor temps.  Mystic/Westerly tends to run a less-drying 5-10F warmer on days like this, but it's calm enough that it was 12F at 7:30AM, only 3F warmer than at my house.  http://www.wunderground.com/weatherstation/WXDailyHistory.asp?ID=KCTMYSTI3 )

Bottom line- in your climate zone in a house as tight as yours drying issues simply won't be a problem.  At 6k' of altitude in Alberta or MT, yeah, think about it, but not on the deck in CT right next to the humid warming ocean breezes.

Thanks for all the input. I'm going to hold tight then on installing any steam humidification (General Air, etc.) units.

Regards,

Jeff