New furnace causing window condensation question


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Old 11-18-08, 09:49 AM
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New furnace causing window condensation question

Hi: We just had a new HE furnace and A/C installed in Sept and for the last three cold nights, we have had to wipe all our windows upstairs( bungalow) due to lots of condensation forming.We had a little last year,but seems waay more this year. Since the new furnace takes combstion air from outside and exhausts outside,the house seems to be more tight, so how do I fix this problem?.The humidity was 67, so I put the blower on continuously and now it's 57. We turn the furnace way down during the night and close all the windows with mini-blinds,They don't seem too bad during the day(fairly dry) just during the cold nights that they sweat! The windows are not that great, but never had this problem with the "old" furnace! Thanks, Huck
 
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Old 11-18-08, 02:45 PM
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try setting the RH back to 50% and keep in mind most of the humidifier is dependent on the heat of the furnace running not just the fan
 
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Old 11-18-08, 05:50 PM
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Originally Posted by sminker View Post
try setting the RH back to 50% and keep in mind most of the humidifier is dependent on the heat of the furnace running not just the fan
Thanks! That's the whole problem...I don't have a humidifier on my furnace. I am trying to get rid of the humidity!. Thanks, Huck
 
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Old 11-18-08, 06:01 PM
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I TRIED.......is the new furnace running low speed in the heating mode(same as old one),and is the air being discharged into the rooms hitting the windows?the return....is it ducted back to the furnaces..no crawl spaces there
 
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Old 11-18-08, 06:28 PM
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New, higher efficiency heating systems in tightly built homes can lead to higher humidity levels. Most of the humidity is generated in the home. Run vent/fan during and at least 20 minutes after bathing. Run range vents during and after cooking to exhaust humidity. Use dehumidifiers to reduce humidity levels inside the home.

Warm air contains moisture. Warm air rises. That explains why the problem with condensation on windows tends to be only on upstairs windows.

Read your owner/operator's manual. It is becoming a common design practice to run furnace blowers continuously at a low speed during the heating season, to improve both comfort level and furnace efficiency. You indicate that humidity level reached 67 with blower off and then 57 with blower on. Humidity level is best if maintained 35-55% year round. If you leave the blower on at low speed, then you can likely resolve your condensation problems.
 
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Old 11-18-08, 07:16 PM
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Thanks! I went with a HE furnace to save money.....now everyone suggests running this and that, where is the savings!! lol!Thanks, Huck
 
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Old 11-18-08, 07:28 PM
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Are these windows single pane windows?

Give it time, when winter is here, the humidity will start going down.

do you run the bath fan when you shower?
 
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Old 11-18-08, 11:55 PM
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If you continue to be in doubt about the efficiency of your furnace operation, and humidity levels, contact the manufacturer. The savings comes with more efficient operation of newer appliances. Your issue was condensation, not savings. The cost of running the fan continually involves minimal cost. Running fan tends to be the recommendation for most modern gas furnaces. Some HE models offer variable speed fans and offer less energy consumption. Thus, continual low speed setting for fan is recommended for comfort, humidity control, and low energy consumption by most manufacturers. Contact your manufacturer for helpful hints.
 
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Old 11-19-08, 06:13 AM
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Windows that have condensation in the heating mode is a sign that you need more ventilation. Increase ventilation until condensation is gone. Like all ready stated Make sure you run bath fans for at least twenty minutes after bathing
 
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Old 11-19-08, 06:19 AM
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Thanks! This morning it was 23F outside and the house temp was 62F with 54 humidity. I have the furnace blower on continuous and I think it helped with the windows sweating a little! The furnace came on and the RH went up to 57. I will tell the wife to run the oven exhaust fan whenver she/we use the stove. Maybe this 21 year old house is starting to dry out!? The windows saty relatively dry during the day with the blinds opened up.( windows are old, so that causes some problems, I would think) Thanks to all who replied! Huck
 
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Old 11-19-08, 03:55 PM
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Yes, old windows and with the blinds closed will cause the window to have condensation on it. The closed blinds makes that space in between much cooler, and makes the humidity to rise more in that area.
 
 

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