Humidity

Mark Hunt

Even radiantly heated homes have convective air movement. You can't stop it completely.

I do not care what you are using for a heating system, it makes no difference.

Moisture levels in ANY structure are influenced by two things, amount of moisture produced and rate at which they are removed.

How does a furnace remove moisture from a building when a boiler will not? They both burn. The air that floats through your house after going past a furnaces heat exchanger is still loaded with moisture. The one and only reason that a structure dries out is because the moisture is leaving faster than it is being reproduced. the only reason a structure will not heat up is due to BTU's leaving at a greater rate than they are being reproduced.

Homes have things like refrigerators with fans on them. Convective air movement. Clothes dryer? Convective air movement due to depressurization. Bathroom exhaust? Air movement. Etc.............................

While a radiantly heated home may have lower convective loss than a warm air home of similar construction, that number is minimal.

Build it tight and vent it right.

I guarantee you that a home insulated with Icynene will be air tight regardless of the heating system. Without HRV, it would also be a terrarium.

Mark H

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J Matthers_2

Humidity

Has anyone dealt with questions on very low humidity levels from HO’s with any of their radiant installs? I have an average of 25% humidity in the house with cooking and showers whish is far lower than I would like to see. The heat is great but the dry air is a killer. I have an HRV and am looking at installing a humidifier to that to keep the level at about 45-50 %. The weather here in the NE hasn’t helped.

BillW@honeywell

If you have ductwork for AC...

> Has anyone dealt with questions on very low

> humidity levels from HO’s with any of their

> radiant installs? I have an average of 25%

> humidity in the house with cooking and showers

> whish is far lower than I would like to see. The

> heat is great but the dry air is a killer. I

> have an HRV and am looking at installing a

> humidifier to that to keep the level at about

> 45-50 %. The weather here in the NE hasn’t

> helped.

BillW@honeywell

If you have dutwork for AC,

you can use a steam humidifier, arguably the most accurate and effective type of humidification. It doesn't require a call for heat to operate, and it controls the fan. If you are installing an er/hr ventilator, remeber they are only about 80% effecient, and some occupants may find the discharge cold, especially on very cold days. The remedy is a small reheat coil, which will temper the air coming from the ductwork, set it up so that it is active only when the temperature is below 32 degrees. Our model is a HE440A1005, which includes the humidifier, control and water treatment kit. Available from any Honeywell PCAD or EED. No retail equivalent.

J Matthers_2

The AC is Unico with hydro coils that could heat the air during the heating season. Will your system work with unico? My HRV is the Lifebreth 300DCS. If I could use the Unico, that would solve the "cold air" problem.

Art Pittaway

Aprilaire 760?

I think is the fan powered unit. Installed on the Unico air handler it will provide the humidity. I believe Unico has a recommendation or solution available. This was used on a $6.5+million all radiant house project and I understand it worked just fine. Call for humidity would turn on the heat and humidifier and a time delay ran the fan for XX minutes to clear the ducts of any moisture. Make sure it is located where you can service it and drain the run off from the pad. I prefer hookup to hot water, one step closer to evaporation.

JimGPE_3

Tweet! Time Out on the Field!

25% Relative humidity might be all you can maintain in the house with weather in the teens or single digits. You will only be able to raise the dewpoint in the house to the level of the coldest surface in the house. Usually that's your windows.

Any more humidity and it will condense out on the windows, so whatever humidity you pump in to the house condenses out on the glass just as fast as you add it.

Worse yet, it may condense in the walls and ruin the framing, sheathing or siding, and you won't know about it until you have a construction failure.

Don't be too quick to start pumping live steam into this house!

With 25% relative humidity, is there any condensation at all on the windows? If so, 25% is it at that outside condition.

Just a thought.

J Matthers_2

No condensation on the windows. House is very tight,SIP construction with all low-e windows. Interesting point, however in the past in the last house with forced air and humidification I was able to keep the humidity higher with no condensation. Graanted, we haven't seen a month of weather in the teens and 20's in a long time.

BillW@honeywell

Without seeing more of your system,..

I would give a reserved yes. The steam unit doesn't require a call for heat to operate, if it senses low humidity, it will start itself and the fan to distribute the humidity. Check it out at www.honeywell.com/yourhome/

David_5

Steam humidifier

I had a customer living in a condo who wanted 55% all the time. We put in a steam humidifier and he loved it. Until the electric bill came in. We then installed a Carrier humidifier that has its own fan, but mounts in ductwork. It works pretty good and is fed with hot water as suggested. The guys steam humidifier is wired in series with an outside thermostat to prevent it from running whenever the outside is warmer that thermostat setting.

David

Mark Hunt

You need


to have a blower door test done.

The heating system has absoutely nothing to do with humidity levels in a home.

Moisture levels are directly connected to air infiltration, period.

I do not think your house is as tight as you think. A blower door test will prove it one way or another.

Mark H

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Boilerpro_3

I'm with Mark on this one

I think your low humidity is a symptom, not the problem. My 2800 sq ft 1906 home with original windows(weatherstripped windows) and extensively tightened and insulated walls is now holding 36% with only two occupants and -10F outdoor temp. Sounds like you are leaking alot of air. If you have ductwork in the attic this is the first place I'd check. Also recessed lighting is generally a huge source of air leakage... I try to avoid it like the plague.

Boilerpro

J Matthers_2

House is new construction with sip panels, all windows low e double pane and foamed, all doors weatherstripped and foamed, no high hats in second floor ceiling...the house is tight. Having said that, I would love to have a test done to see what I may have missed, there is alwas something. Of course, now that I think about it, the house has five flues. That could be a factor as well as the great evening fires we have each night. I have yet to install the range hood and a gas fireplace in the master. Once that is done I'll balance the HVR and have a test done. Whether or not I have areas I can tighten, I will sill have three fireplaces and a brick oven and air exchange via the flues. So, I will likly still have low humitity in the winter.

I agree, RADIANT heating will not effect the humidity levels in a house, however forced hot air without a humidifier certainly will.

tombig

You mean

that HUMIDISTAT setting... stop confusing me!! I'm still looking for a stand alone, single unit programmmable T-stat that has built H-stat to activate a steam generator and air handler. Simple enough!!

Honeywell stat seems part of 'Perfect Temp System'. I'm looking for a simple programmable T-stat with H-stat built in. I can't believe no one but Carrier makes it!!!!!!!!!!!!!!

Greg Swob

We have installed several

Carrier/Bryant Thermidistats and customers like them. Relatively simple to program, lot of functions and capabilities depending on needs. I'm sure other makes are available, but this is the only combo temp/humidity in-one controller I am presently aware of. No customer complaints so far. Greg