Condensation around windows...

Have a new build single story addition I'm working on, I have a gas temporary heater which maintains the temp to around 50+ degrees and a couple fans to move the air flow around. My windows are in, weather taped on the outside and insulation around the inside until I install my window jams and fill with window foam. I live in a cold winter climate and when the temperature goes well below freezing I'm getting condensation around the bottom of the windows, only if the temp goes below freezing. Could this be caused by the inside of the addition isn't warm enough or maybe high humidity? The inside walls are dry (not damp) only getting condensation around the bottom of the windows. Should I increase the heat, crack the windows open a bit for humidity reasons, more air movement? Any info would be appreciated...

 

I assume your heater is not vented outside and burns propane. It will put tons of moisture into the air when it's burning.

Cracking the windows won't really help since you'll have to run the heater more to keep the temperature up... adding more moisture to the air that needs to be removed. It's a curse of vent free heaters. A major by product is water.

 

My first guess would be the same as Pilots.
I tried using a gas unvented fireplace in my living room and within an hour all the windows where covered with water and there was water dripping off the ceiling.
I replaced it with a vent one and never had another issue.

 

We have friends that have an unvented fireplace in their summer home. The house is only used occasionally during the winter but they keep the heat on around 50*-55*. Last spring they had to hire a painter to clean up the mold and repaint.

 

It sounds like you're in the process of building and the non vented heater is temporary.
That should be ok for temporary use.

 

You can also get a ton of frost buildup behind the insulation when its very cold out and you are heating with an unvented gas heater, before the drywall is on. All the moisture will freeze on the interior side of the exterior sheathing.

 

Everything is all completed in the addition, only thing I have left to do is install my window jams and put the molding around them. I was leaving putting in my furnace last seeing I had temp heaters, I didn't know the unvented heater would cause moisture problems, don't really want to install the jams if I'm going to have water dripping on them the rest of the winter, I'll have to try to figure out some other kind of heat until I can install my furnace. If I was to use a dehumidifier would that help?

 

A dehumidifier would help.
At this point your windows/frames should be well insulated..... that will help too.

 

As an added bonus most of the electricity used to run the dehumidifier will be turned into heat so you'll get double use out of your money; dehumidifying and some heat.

Humid air is less dense than dry air so it would help a bit if you can put the dehumidifier somewhere up high. Or, have a fan in the room aimed upwards(ish) to stir the air in the room.

 

We have below 0 temps coming again this weekend, going to buy a dehumidifier today. I'll also put a fan in each room aimed upwards to keep the air moving. If I understand everything correctly the longer the heater runs the more moisture it will produce? Should I lower the heat to a minimum so it doesn't run that long?

 

Lowering the heat is also making your glass colder. The colder the glass is, the worse your condensation will be. My advice would be to raise the temperature, run the dehumidifier constantly (get the largest one you can afford and be sure it has a bilge pump that will pump the water out) and run fans to circulate the warm air. I would point fans at windows, not at the ceiling... this also will warm the glass.

Assuming you can lower the humidity, the warmer you can make the glass, the less chance you have of the dewpoint and glass temperature crossing paths.

 

Got a nice big dehumidifier, gonna set it up this morning. I'll be sure to turn the heat up and adjust my fans towards the windows. Gonna be cold the next couple day, temps in the single digits with a wind chill well below 0, if this dehumidifier is gonna work now's a good time to find out. I do have extra house wrap left, if I cover over the outside windows you think that would possibly help to keep the cold wind off keeping the windows warmer this winter? Just thinking outside the box...

 

I don't know that housewrap would hurt but it wont help very much since housewrap has no r value and you'd have to tape the edges to get the most from it, or the cold wind will just blow in and make the window the same temperature anyway.

 

Ok, just have one more question before I set up dehumidifier. I have the unvented heater in the living room area which is the warmest room, rest of the rooms are warm but mostly the living room seeing the heater is there. Seeing the living room has the heater and it making all my moisture should I put the dehumidifier in the living room or put it in the center of the addition which would be in the hallway near the doorways of the living room, bedroom, kitchen, and front door...

 

Yeah, if that is the known source of the moisture, you could put it there. Maybe there is one end of the living room that leads away from it and toward majority of the rest of the house.

 

I put it in the hallway near all the room entrances towards the front door seeing that part of the house was getting the most window condensation, especially on the front steel door and window. Bought a high capacity 50 pint dehumidifier, placed it in the home around noon yesterday with fans facing towards the windows. It ran about 11 hours and the water collection bucket was over 3/4 full, also ran all night with temps below 0 and this morning the bucket was 1/4 full. When I started the dehumidifier the digital readout on the unit read around 60% humidity, this morning it was down to 43% with no condensation at all on any of the windows or front door.I appreciate all the help, it was the best investment I made to correct my condensation problems, I hope it'll continue doing it's job. I learned a lot about vent less heaters and dehumidifiers this week, thanks again. I'll keep you posted if any changes occur...