Jump to content

Water, water everywhere!


Recommended Posts

I've made some changes to my house which haves drastically affected the way it works - I knew it would.

I've got a good idea on what to do--shoot, I give ideas all day long to my clients--but wanted to pose this here.

To keep it short and simple, I've tightened my house significantly. Air-tight insulation on the ceiling and the sub-floor. Only thing that still "leaks" are the walls.

After these changes indoor condensation on everything skyrocketed. So much that the picture glass windows (single pane) condensate so much you can't see through them and the drip-off is saturating the carpet below them.

How do you think I should control/eliminate/reduce the condensation.

Link to post
Share on other sites

I've made some changes to my house which haves drastically affected the way it works - I knew it would.

I've got a good idea on what to do--shoot, I give ideas all day long to my clients--but wanted to pose this here.

To keep it short and simple, I've tightened my house significantly. Air-tight insulation on the ceiling and the sub-floor. Only thing that still "leaks" are the walls.

After these changes indoor condensation on everything skyrocketed. So much that the picture glass windows (single pane) condensate so much you can't see through them and the drip-off is saturating the carpet below them.

How do you think I should control/eliminate/reduce the condensation.

ERV

Link to post
Share on other sites

I've made some changes to my house which haves drastically affected the way it works - I knew it would.

I've got a good idea on what to do--shoot, I give ideas all day long to my clients--but wanted to pose this here.

To keep it short and simple, I've tightened my house significantly. Air-tight insulation on the ceiling and the sub-floor. Only thing that still "leaks" are the walls.

After these changes indoor condensation on everything skyrocketed. So much that the picture glass windows (single pane) condensate so much you can't see through them and the drip-off is saturating the carpet below them.

How do you think I should control/eliminate/reduce the condensation.

ERV

First find out about your indoor humidity levels with accurate measurements over several days, not just guessing.

If the levels are high, then a heat recovery ventilator and/or dehumidifier.

In any case, modern thermopane windows will reduce or eliminate the window condensation but I'm more concerned about what is happening that you can't see (inside the walls) than the condensation on windows.

Link to post
Share on other sites

I did the same thing, tightened my old farmhouse so much (about 2.5 ACH50) that now we have a lot of humidity. We have dual glazing but still get some condensation on the bedroom windows in some cases. The answer is to run a bath fan enough to remove the humidity. This can mean several hours per day. You should have a hygrometer to keep track of things. I installed a Panasonic WhisperGreen fan, rated for continuous use, with a low/continuous setting of 30 CFM (can by adjusted up) and a full speed of 80 CFM (when you hit the switch).

A HRV retrofit may be worthwhile, if you have a perfect setup for it (probably an open attic with an easy way to run short, clean duct runs that are insulated). The value of the saved heat you can recover is low if your electric rates are like mine, and the cost of the equipment and install is high, but it can do a better job than a single point exhaust fan.

Replacing the windows or adding storms will or course help the condensation, but not the humidity.

Link to post
Share on other sites

Yes, you can get a few of these for $15 each.

Click to Enlarge
tn_201421618501_41qNkSOUG9L._SL500_.jpg

25.78 KB

The ERV/HRV idea is good but when the outdoor humidity is over 70% you don't gain much, except you are circulating the heated air, which is good.

Ceiling fans are easy to install, good for circulating warm air.

Link to post
Share on other sites

The winter air is dry enough to easily remove humidity if you ventilate the house. It works like a charm in my place, and Randy is ~50 miles away.

One thing I do if I get up in the morning and notice condensation... crack a window in the bedroom and dry a load of laundry. The dryer pulls its makeup air through the bedroom window. Run a load of wash the night before so you have something to work with.........

Link to post
Share on other sites

Yes, you can get a few of these for $15 each.

Click to Enlarge
tn_201421618501_41qNkSOUG9L._SL500_.jpg

25.78 KB

The ERV/HRV idea is good but when the outdoor humidity is over 70% you don't gain much, except you are circulating the heated air, which is good.

Ceiling fans are easy to install, good for circulating warm air.

Those thermometer/hygrometers are so cheap probably because they only measure celsius. . what good is that!

I jest.

Yes, you brainiacs are confirming my strategies, but this is where it gets tricky.

An HRV is my first choice but it will be expensive and I don't have an attic to install it. I have a lowered ceiling over the bathroom (under my vaulted ceiling) in the middle of the house I can install and place sidewall ducts/register on the walls facing in to house. I think that would be ok.

The cheapest option is as David has done in his house -- install a higher CFM and quieter bathroom fan in that same bathroom set to run with a digital timer. I'm not sure that would work as well as the HRV. . . I don't know.

John poses an interesting dilemma in that if the outdoor humidity is 70% plus, then the HRV may not be much benefit; however, 70% outdoor would not stay that high if I brought that air inside and warmed it. The humidity would drop.

BTW, I have dual pane windows throughout the house. I only mentioned the single pane windows as they're the largest and most obviously affected. The dual pane windows condensate heavily as well just not nearly as much.

Most obnoxious are the two new skylights I've installed. They condensate so much that we have to leave a towel on our bed as the dripping would soak the bed covering and mattress on a very cold day.

Any other thoughts?

Link to post
Share on other sites

90% natural gas central forced air.

Maybe do something that's common in commercial: Run a small duct, with a damper on it, from the furnace intake through the ceiling and roof deck to outside, to bring in some exchange air. Not expensive, not difficult, and through trial and error you'll learn which setting of the damper brings the most desirable effect.

Marc

Link to post
Share on other sites

The cheapest option is as David has done in his house -- install a higher CFM and quieter bathroom fan in that same bathroom set to run with a digital timer. I'm not sure that would work as well as the HRV. . . I don't know.

With a HRV, you have the option of pulling air from multiple locations and supplying air to multiple locations, so better mixing of air. With a whole house fan, you have one exhaust point, and makeup air is drawn through the cracks. HRV is perhaps more "surgical".

It sounds like you have something extreme going on there. Is this slab on grade? Wet basement? Air-drying laundry? Fish tanks? Five large dogs and a collection of tropical plants? Someone steaming vegetables for every meal? Other sources of humidity besides the occupants? How many square feet and how many occupants? I wonder if something else is going on. Furnace exhaust is a good suggestion to check.

Link to post
Share on other sites

I've made some changes to my house which haves drastically affected the way it works - I knew it would.

Were you expecting a result other than moisture problems and increased indoor air pollution?

It seems odd to me that after people spend money to make their homes more air tight they then have to spend money to help it breathe.

Somewhere along the line they're not being given the full story when they start out on such projects.

Link to post
Share on other sites

It's not odd. It's smart. Build tight, ventilate right, etc., etc. Doing otherwise is stupid. What're you going to do, build it loose? How loose? No way to engineer loose, lots of ways to engineer tight and right.

On the super tight places we've done, we've discovered that humidifier settings that vary by as little as a single percentage point means the difference between perfection and water running down the windows, even with good windows. It takes a while to fine tune the settings, but it's only time, and once accomplished, everything is fine.

The single largest factor we discovered is bathroom fans. Get a good one and put it on a good timer. It's cheap and effective.

If you did all that tightening up and didn't address other stuff like non-engineered basement, or some other ground water source, then the tightening was putting the cart before the horse. Oops. If everything else is (more or less) equal, bath fans always seem to be the point for us.

After that, an ERV. You can dial in your IAQ like magic.

Link to post
Share on other sites

John poses an interesting dilemma in that if the outdoor humidity is 70% plus, then the HRV may not be much benefit; however, 70% outdoor would not stay that high if I brought that air inside and warmed it. The humidity would drop.

It's not a dilemma. In our climate, the outdoor air is only that humid when it's cold outside. When you warm the humid, cold air, its Rh drops like a stone.

Link to post
Share on other sites

. . . The single largest factor we discovered is bathroom fans. Get a good one and put it on a good timer. It's cheap and effective.

Just finished two projects that used both bathroom and kitchen fans like this. I had not seen the kitchen fans before. They're made by Venmar and are pretty cool. This approach (generally) puts exhaust points on opposite ends of the house. Useful in multifamily projects where you've got large families with grandma boiling cabbage all day in the kitchen.

Link to post
Share on other sites

John poses an interesting dilemma in that if the outdoor humidity is 70% plus, then the HRV may not be much benefit; however, 70% outdoor would not stay that high if I brought that air inside and warmed it. The humidity would drop.

It's not a dilemma. In our climate, the outdoor air is only that humid when it's cold outside. When you warm the humid, cold air, its Rh drops like a stone.

You are correct, sir. The HRV has a drain pan and a drain to send that water back outside.

A house I inspected a couple of weeks ago has a furnace blower fan in a plywood box in the crawlspace. Ducts draw warm dry air from behind the woodstove and blow that air into the lower level bedrooms. I'll post a pic man(y)ana.

Link to post
Share on other sites

The cheapest option is as David has done in his house -- install a higher CFM and quieter bathroom fan in that same bathroom set to run with a digital timer. I'm not sure that would work as well as the HRV. . . I don't know.

With a HRV, you have the option of pulling air from multiple locations and supplying air to multiple locations, so better mixing of air. With a whole house fan, you have one exhaust point, and makeup air is drawn through the cracks. HRV is perhaps more "surgical".

It sounds like you have something extreme going on there. Is this slab on grade? Wet basement? Air-drying laundry? Fish tanks? Five large dogs and a collection of tropical plants? Someone steaming vegetables for every meal? Other sources of humidity besides the occupants? How many square feet and how many occupants? I wonder if something else is going on. Furnace exhaust is a good suggestion to check.

I believe the only extreme factor in my house is 6 of us living in 1,600 sf!

Crawl space is dry but I've sealed the underside of my sub-floor with 1" of spray foam, so I'm pretty sure I've de-coupled the two spaces.

Furnace is located in the crawl space and direct vents outside.

We've already got exhaust fans in each bathroom for showers and such.

Based on y'alls feedback, I think I've solidified my plan of attack using an HRV.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...