CONDENSATION ON WINDOWS

[Anonymous Poster]

Lane, I moved from the house with the heat exchanger 14 years ago and built it 6 years before that, so some things are a little hazy, but here goes. I measured the air flow capacity and it was about 100 cubic feet per min. of both flow into the house and flow out of the house. The exchanger had 2 fans, one for inflow and one for outflow. The house was about 1800 sq ft of heated space. Once the moisture level stabilized I would run the heat exchanger on a timer for about 6 to 8 hours a day during heating season. Before I installed the heat exchanger, each morning there would be big puddles of water on each windowsill, sometimes dripping onto the floor. I would saturate two bath towels wiping up this water each day!

I located the interior intake ducts to draw air from the bathroom and kitchen and exhaust outside. The fresh outside air after heating was discharged into the basement where the wood stove was located. The wood stove had it's own fresh air supply from outside so it did not create negative pressure in the house and interfere with the flow balance in the heat exchanger. I installed thermometers at the inlet and outlet of both heat exchanger airstreams and used the measurements to calculate the efficiency. If I remember correctly the efficiency was around 90% and when the outside air temp was in the teens, the incoming air would be warmed to around 60 degrees. This is better performance than most commercial models. The higher efficiency is do to low airflow rate coupled with a very large heat transfer area.

Not having much money at the time, I built the heat exchanger from inexpensive but effective materials and a large heat transfer area. I used heavy duty aluminum foil with stryofoam spacers to make the core of the exchanger and it was housed in a wax lined plywood shell. I used it for 6 years before I moved and it was in perfect condition without ever requiring a repair when I left.

The heat exchanger worked so well I created plans, advertized and sold about 350 sets of them in a year or two. That was quite a few years ago.

Hope this answers your questions,

Andy

 

[Lane]

Andy, are any plan sets still available for purchase?

 

[heehaw]

some areas of the country need vapor barriers installed and some don't, this area needs vapor barriers; even if the dang thing didn't work and wasn't needed, i would put one in, because..@4 years after we built this house, one of those little arkansas tornadoes came by and removed part of my roof; we had water dripping from some of the light fixtures, but we did not have a single spot on the ceiling; granted it took me several times that summer of turning the blown in fiberglass insullation to get it dry, but that was a lot easier than replacing ceilings..i check my attic a couple times a year, one was about 2 weeks ago, right after we had @7 inches of rain; one of the seals around a 3inch vent pipe was found to be leaking, i followed the water stain down the pipe to the top of the stud wall, where, without the "vapor barrier" we would have had a stained ceiling, but with it, i was able to move the insulation around, and repair the vent seal, and was done..
heehaw

 

[heehaw]

the first house i built, i installed double pane, aluminium frame windows; we had central gas heat; in the winter, we used insulated curtains on all the windows, and we would have ice on the inside of the windows every morning. I installed storm windows on the outside of the windows after @3 years of putting up with the ice/moisture on the windows; a vinyl spacer was installed between the metal frames, to stop the heat/cold transfer; we never had moisture/ice on the inside of the windows again..
heehaw

 

[rdln]

make sure clothes dryer is properly vented to the outside. my $.02

 

[Anonymous Poster]

Lane, I will have to check to be sure, but I think I still have copies of the plans. I will be buisy putting a fence this weekend, so I will check early next week and let you know if I still have some.

Andy

 

[kiphorn]

Several years ago I had the opposite problem. My house was so dry, everyone was suffering from dry skin /w3tcompact/icons/frown.gif. In invested in a small wireless weather station from <A target="_blank" HREF=http://www2.oregonscientific.com/cablefree/bar112hga.html>Oregon Scientific</A> that had indoor temp & humidty readings as well as a small sensor that is placed outdoors for reading outdoor temps.

I think I bought mine at
<A target="_blank" HREF=http://www.weathertools.com/oregon.htm>Weather Tools</A>

When I got my weather station I was running at about 19%-22% relative humidty in my house. I added a humidifier to my furnace and now run at a comfortable 40% /w3tcompact/icons/smile.gif.

Kip

 

[jimgerken]

We HAVE engineered a system, It's called Tyvek. Tyvek works like Gortex, allowing moisture vapor to escape, and yet keeps out liquid. Tyvek (or its competition, Typar) are used on all houses in Minnesota. The Tyvek goes on the outside, and the inside is a poly vapor barrier. There doesnt seem to be any concern with the reverse condensation happening in the summer as someone mentioned in an earlier post, I suspect this is 'cause the temperature differential is not as high. As long as there is nothing blocking it on the outside, the wall keeps drying.

CONDENSATION was a major problem in my house after wrapping and residing and all new energy efficient windows were installed. Before all this, the leaking windows sucked all the humidity out (and let snow drifts form on the kitchen counter). We priced the smallest heat exchanger and parts alone was a couple thousand dollars. Instead, we added a forced-air fresh air intake blower to continuously bring in 100 CFM. It brings cold dry outside air into the house from a screened vent hood located high on the east side of the house. There is a standard furnace filter in line before the small blower, to filter out the insects and dust. The blower is a surplus item I found and adapted, about 100 CFM. The output of the blower feeds the cold air return of my system, just before the air travels to the main furnace filter. This fresh air blower is running all the time, from late Fall till Spring, to keep indoor air quality higher and keep humidty down to eliminate condensation. It also helps lower Carbon Monoxide and Carbon Dioxide and helps eliminate odors. It may seem strange to tighten up your house so much it needs fresh air forced in, but unless you are a really good guesser, you need to go too far and then come back with supplied fresh air.
This little almost silent blower has cured our condenation problems for a cost of a couple hundred dollars, plus a few pennies a day operating cost. Any questions, just ask.