I've written about HRV's now several times on the board, I'll try to find the posts where I've done so, so that I can point to those as well.
Basically - the HRV will solve your humidity problems (assuming your outside air is less humid).
An exhaust fan will draw the air out - but if you don't replace the air going out, you have an air deficit. This can be a problem. First of all, it means your going to be heating your house more than you should. Secondly, if the house is too air tight then that air is going to come in through whatever means it can - and as Aussifishy pointed out - this can be a serious threat if if comes in through a furnace exhaust vent.
Stove top fans, for example, over a certain amount of cfm, building code requires that there be interlock with the furnace. Ie. if the fan is on, so too is the furnace.
I had BIG BIG humidity problems in my house. The HRV solved them. It runs on a dehumidistat (opposite of humidistat) so that if the humidity of the house EXCEEDS a threshold, the unit turns on. This keeps your household humidity in control.
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Originally Posted by Joe Reefer
HRV's are only an option to reducing heating costs by recovering some of the heat being exhausted. To elimate moisture issues you must "exchange air" simple as that.
If you are truly serious about not having any moisture issues, a make-up air system should be considered. This would include a small furnace with a stainless steel heat exchanger to draw 100% fresh air from the outside, there would also be an exhaust fan interlocked with the furnace. The cfm output of the furnace and exhaust fan should be close in performance. An HRV can then be used on this to recover some of the cost running this system when its -40.
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Not quite correct, Lando. The HRV is a heat exchanger AND an air exchanger. It pulls air out of the house, and draws air INTO the house.
You shouldn't need a second furnace - the HRV, if sized correctly, can and WILL solve the humidity problems.
Quote:
Originally Posted by phillybean
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They work, but they're noisy and the effect is localized. And as soon as they stop, the humidity goes right back up again. I ran one for years and it only helped reduce the problem but it did not eliminate the problem. The HRV did solve my wet windows/wet walls/mold/mildew problem.
Pricey yes, but ... it is littlesilvermax said. Once your house has black mold, you may as well burn it down. This is the reason that grow houses tend to be condemned - the humidity just ruins the house and it becomes a health hazard to those who live inside it. Our aquariums might not do the same amount of damage but, humidity is humidity. So pricey it may be, but if you have excessive humidity then it becomes the price to pay to stay within the hobby.
You can buy HRV's at Home Depot and install them yourself if you're handy with DIY. You can also call a HVAC place and have them do it.
I had a place recommended to me by another Canreefer and I would recommend the same people. They did an excellent analysis of the amount of humidity, the volume of the house, required turnovers, and came up with a unit sizing recommendation. Anyone in Calgary considering a HRV, PM me and I will give you the contact information.