Basement Humidity Issues

Unknown

changing boilers from atmospheric to sealed combustion mod-cons(outside air intake), affects air movement/permeation in an older home, has anyone had any complaints about excessive humidity showing-up on their windows?<BR>How do you guys handle that question from the H/O?<BR><BR>Dave

Brad White_202

Control

Man, I hate unintended consequences!

Any atmospheric boiler will draw twice the air it needs as you well know. Never thought of them as a basement ventilator specifically but what you say rings true.

I would tell the H/O that at least they can control the basement humidity independently and to a setpoint using targeted ventilation (operate a fan on high RH but only when the outside specific humidity is lower than the inside), or use a mechanical dehumidifier.

I see that situation as a plus, illustrating what uncontrolled leakage they once had. With my atmospheric boiler gone and sealed combustion installed, my basement is a lot warmer I grant you that.

Keith Johnston_2

What do you use to measure outside specific humidty?

I have always wanted to run my HRV only when the outside air was drier than inside, but have never figured out how to measure the outside humidity level without needing a computer to do the calculations.

Brad White_202

If you do not use a computer

then use a slide-rule!

Actually, a couple of ways and it takes a computer, a small PLC controller at least.

One way is that I specify is to use the psychrometric tables from Linric (great resource and company) as the database and it compares absolute or specific humidity indoors and out, taking the lower of the two as being the trigger.

The other way is to use an enthalpy controller, same deal, lower energy level of the two. I have seen this done with packaged Honeywell economizer controllers which use enthalpy, not just temperature. That I think is the least costly way to do it right.

Naturally the cost factor will determine if it is worth doing; if on higher end housing or a Habitat house, you make the call.

As you obviously know, relative humidity has nothing to do with it; it is the specific or absolute humidity that seeks to dry.