This is the only forum that this question fits in, so here goes.

Today I consulted on a 4 year old log home with very high humidity. Here is some background.

• 4 year old log home (very well built)
• foam roof panels, no attic
• Superior Wall foundation
• Hot water heat
• Logs are 13% moisture

They are running 4 dehumidifiers 2 of them are through the wall Air Conditioners while also trying the heat the the home with the boiler. The home owner says "if they shut them off, humidity rises to 65% within hours". With all 4 running they can only get ti down to 50%.

He taped plastic to to the basement floor and it remained dry. I did an infrared scan and found nothing unusual.

Please help with your suggestions.

Bruce

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Bruce - The home is 4 years old - has this been a problem all along, or is it new?
Are you sure those are DE-humidifiers they're running? Just kidding.
Gas appliances backdrafting?

John,

Yes it has been a problem all along. That's why they installed the A/C units. A first they thought it was just the logs drying out but it never reduced.

Gas appliances is a good question but they are power vented.

Bruce

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Hi Bruce, a few questions?????

How many people live in the home?

Is the humidity higher inside the home when compared to the outside?

Does it matter what time of year it is?

Is the home tree shaded?

What was the humidity in the basement? In the living area?

Do they take showers or baths? Are the bath's vented to the exterior?

Do they have a sauna?

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Scott Patterson
Spring Hill, TN
http://www.traceinspections.com

Condensation on the Hot Water Heat.

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Billy J. Stephens HI Service
Memphis TN.

Scott
How many people live in the home? 2

Is the humidity higher inside the home when compared to the outside? I don't know but I'll find out.

Does it matter what time of year it is? They said summer when they have the windows open it's not a problem.
Is the home tree shaded? No, it's in the woods but on a cleared area.

What was the humidity in the basement? 40% In the living area? 51%

Do they take showers or baths? Showers Are the bath's vented to the exterior? Yes

Do they have a sauna?No

Billy,
I didn't see any. All copper clean and dry.

Thanks guys,

Bruce

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A quick google of Average Relative Humidity shows a yearly average of the 6 PA cities listed of Allentown 56%, Erie 66% and Oct,Nov,Dec in the 70% range 50 to 65% does not sound unduly high.

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Billy J. Stephens HI Service
Memphis TN.

That is RH of outside air. As the outside temp drops teh airs ability to hold moisture decreases. As the air is brought inside and is heated it's RH goes down. 50-60% indoor Relative Humidity would be quite high in the winter.

example:

If the outside air temperature in winter is 0°F and the relative humidity is 75 percent, that same air inside your 70°F home will have a four percent relative humidity. That’s dry! The Sahara Desert has an average relative humidity of 25 percent.

Humidity and the Indoor Environment

00
Michael,
So the human body is comfortable with a humidly of between 20 & 60 percent,

The complaint is High Humidity in a tight Home (Logs read 13% doesn't sound like it's building up to cause any moisture damage.)

Solution to a home owner complaint is to ventilate the conditioned space.

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Billy J. Stephens HI Service
Memphis TN.

The installation of HRV is suggested assuming there is no unusual source found for the offending moisture.

Michael,

And what might the unusual source be in this case?

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Billy J. Stephens HI Service
Memphis TN.

IF there is one it is unknown at this time.

Billy, chill out. For all I know they each take three showers a day and forget to use the bathroom exhaust fan. Do you know more?

Thanks guys,

I was thinking HRV but I wanted to be completely sure because of the cost to install and operate.

Another detail:

One of their complaints is that several (not all) of the windows get condensation build up at the bottom. He said "If I don't run the dehumidifiers you won't be able to see out of that bay window".

Bruce

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What is the SQ Ft of the home?

What is BTU or Ton on A/C? X2

Reason I ask over size A/C will produce more moisture than remove.

Did a moisture analyst on a 3500 sq ft with 2 central HVAC systems. They had (1) 2.5 ton unit cooling about 900 sq and water was running out of the supply registers. And the HVAC pro just cound not figure it out?

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Chip
Destin,Fl
"The only non-addressable objection is the unkown"

That's classic high humidity in a home in colder climates. In fact if there is a rapid temperature drop outside it will happen anyway. The cost of running the HRV should be a lot less than running dehumidifiers in the winter.

You could recommend some experimentation to locate the source of the humidity.

"He taped plastic to to the basement floor and it remained dry."

My first experiment (after the above) would be to do the same to the basement walls. If moisture is coming in the walls (were not sealed properly, or maybe not at all), then that is the problem. It may be one wall, or one section of one wall.

After that, you could try other things: Do they have a fireplace they could use for heat while shutting down the heating system (although I doubt the heating system is a problem, but the intent is to isolate non-problem items from the list), then start with other equipment, exhaust fans, etc. Maybe they have too large of exhaust fans and are pulling a negative pressure on the house, which is in turn sucking air (and moisture) from wherever it can.

Maybe installing this would allow them to pressurize the house without using unduly cold outside air to do so. See if one can be rented and install it through a window at the basement.
Air-to-air heat exchanger
An air-to-air heat exchanger mechanically ventilates and dehumidifies homes in colder climates. During the winter it transfers heat from the air being exhausted, to the fresh, outside air entering the home. Fifty to eighty percent of the heat normally lost in exhausted air is returned to the house. Air-to-air heat exchangers can be installed as part of a central heating and cooling system or in walls or windows. Wall and window-mounted units resemble air conditioners and will ventilate one room or area. They are easy to install.

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Jerry Peck, Construction / Litigation Consultant
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