# high humidity in basement



## pF45 (Jul 23, 2008)

I'm not qualified to repond, however check your gutters sounds like water is not being diverted away from the house when it rains. This can cause humid and moist environment in basement even water on the ground. Also is your ac unit drain clogged in the basement. That will back up if clogged. Hope this was somewhat helpfull. Sounds like you should find the source of the moisture and tackle that before anything else. Good luck:thumbsup:


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## orange (Feb 19, 2008)

pF45 said:


> I'm not qualified to repond, however check your gutters sounds like water is not being diverted away from the house when it rains. This can cause humid and moist environment in basement even water on the ground. Also is your ac unit drain clogged in the basement. That will back up if clogged. Hope this was somewhat helpfull. Sounds like you should find the source of the moisture and tackle that before anything else. Good luck:thumbsup:


Thanks for your response. We did adjust the downspouts. They were going into the ground ( could be connected to weepers - we don't know) but seemed to be going to a dry well -pit with gravel. We put elbows above ground and put 8-10' of plastic pipe on each to run the water from gutters down the sloped lawn.

Note house is relatively high with lawn sloped away from the house on all sides.


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## ccarlisle (Jul 2, 2008)

I would definitely either have the furnace fan running constantly (if it is capable and rated for 24/7 running) OR have the Venmar running. 

The idea, apart from the idea just suggested in the previous post is worthwhile; you have a high humidity problem, the source of which you will have to find, but if you don't find one then you just have high humidity. Maybe coming in through the concrete...could be a number of ways. But one way to reduce mould and musty smells are to increase ventilation in the house specifically in the basement and if possible vent that outdoors. 

There is a chance that a previous water accident left mould in the furnace ducts, in which case a good professional cleaning is in order. But your house would have smelled a long time a go if you had, so I would reduce that probability. No I'd say you had -or have - higher than 60%RH conditions with no air movement and thus mould growth.

Clean it up with dilute bleach, put on the air exchanger and get a dehumidifier if you like. Don't do all that much but every little bit helps...


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## orange (Feb 19, 2008)

ccarlisle said:


> I would definitely either have the furnace fan running constantly (if it is capable and rated for 24/7 running) OR have the Venmar running.
> 
> The idea, apart from the idea just suggested in the previous post is worthwhile; you have a high humidity problem, the source of which you will have to find, but if you don't find one then you just have high humidity. Maybe coming in through the concrete...could be a number of ways. But one way to reduce mould and musty smells are to increase ventilation in the house specifically in the basement and if possible vent that outdoors.
> 
> ...


Thanks. They did install a dehumidifier last night and it is working well. Also, they are running a fan in basement window to exhaust air from basement. 
There has been no musty smell in the house. I think a big factor is that we have had the wettest June and July in years- and rain is predicted right through to next Monday. It' hard to dry anything with these conditions. And it's raining right now. Seems the Venmar would just bring in the humid air.

Is there any danger of worsening the situation if they turn the furnace fan on at this time?


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## 8 Ball (May 17, 2008)

Is your Venmar an ERV model, or an HRV. Model number will help. Just currious why the tech said it was not necessary to run it during the summer.

I know in Canada, they are desirable, due to ventilation requirements, and it is more likely the previous owner experienced similar problems and dealt with them by installing the Venmar ststem. Some are more elaborate than others, and do offer dehumidification. Try turning it back on, and see if it helps.

Just read your post re. Venmar system... never mind, probably a simple HRV.

Thanks.


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## orange (Feb 19, 2008)

8Ball,

System is Venmar Constructo 1.5 Model 43110 Installation date Nov 2004.

Does this help?

Is there a procedure for running/setting this?
Thanks


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## ccarlisle (Jul 2, 2008)

Well, it sounds as if the Venmar just brings in new air from outside, runs it through the furnace and the exhausts it. OK, that's fine too. At least it's moving...

If the RH outside was constantly above 60% at 21 deg C, and the same conditions were inside your house but there was little air movement, then mould would grow wherever it found food. Mould growth can be reduced by: 1) reducing the moisture content of the air; 2) increasing air movement or 3) increasing the air temperature (either the general space temperature or the temperature of the walls and floor).

Either high humidity or temperature can be the major factor in a mould problem. A humidity sensitive mould may not respond well to increasing temperatures, and conversely a temperature-sensitive mould may not respond very well to increasing ventilation. So try both increasing the temperature down there and reducing the humidity by increasing the ventilation.

If the relative humidity near the middle of the basement is fairly high (e.g., 50 percent at 20 deg C), mould or mildew problems in the room are likely to be humidity level-sensitive. If the relative humidity near the middle of a room is fairly low (e.g., 30 percent at 20 deg C) mould or mildew problems in the room are likely to be temperature sensitive.

Good luck!


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## KUIPORNG (Jan 11, 2006)

*Inspect all Basement Walls*

there may be a small leak.... look at the bare concrete.... a leak is not a big deal... it can be fixed easily most of the time.... not knowing/and finding it is....


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## 8 Ball (May 17, 2008)

ccarlisle..

Is this a probable case of ground saturation? Does saturation increase w/depth of the soil, or is it less. I know she has stated that the ground is sloped away from the house, but without knowing the depth of the basement vs. the depth of the slope, at what point do you consider improving the terrain vs sealing the entire basement?


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## ccarlisle (Jul 2, 2008)

Yes, I think it is a saturation issue, thankfully a temporary one. I didn't ask if they had a sump pump, it may be there isn't one and that their house is close to - or now at - the ground water table. But the drainage issues are always IMO the first fix before tinkering around indoors...indoors you just see the effects of inadequate-fix causes outside.

So the downspout directed away from the foundation is a good start unless you can be absolutely sure the water goes deep enough into the weeping, the weeping isn't blocked and the proper sock around it and that that runoff is properly connected to the sewer. There are a lot of "ifs" and I'd just rather see a 8-foot pipe taking the runoff away from the house altogether. They have that...so fine. 

That's all part of positive-side remedies. On the negative-side i.e. inside the house, I like to apply a silicate sealer to concrete. If that's not feasible (and most times it is), then you can always do what's happeneing here: manage the humidity levels to provide a safe, mould-free living environment. I personally think fans should always provide adequate air circulation, and the Venmar is just one I like.

Saturation increases with soil depth.


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## orange (Feb 19, 2008)

The house does have a sump pump. It has been working during the actual rain, but after the rain the sump pit is pretty much empty. I have a feeling there is some saturation next to one wall - under the front porch. The plan is yo remove some porch floor boards and see what the grading is like, We think this may have been saturated because of all the rain and the way the gutter drains were set up.
The dehumidifier is working great. RH is in 69-70% range.​
Prediction for today is sunny with no rain !!! Maybe we can dry out a little.


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## ccarlisle (Jul 2, 2008)

Well, well, orange, you're from my home town! Was born in Rockcliffe Park.

RH of 70% at say 17 deg C is OK, but still a bit high. Can't do much else but to run the dehumidifier because outside it's probably 75%RH at 22 deg C. But as soon as it gets to around 55%RH at 23 deg C, then open doosrs and windows, run the Venmar because then you'll be removing the moisture naturally. The the mould problem will go too.

Nice and sunny here today! We're about 125 miles apart


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## orange (Feb 19, 2008)

After installing a dehumidifier and some ceiling fans RH is now about 53-55%.
Things seem much better.


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## ccarlisle (Jul 2, 2008)

Good...the next things you'll want to look into is continuous air movement down there - which you may already have with the Venmar - and removal of sources of mould growth i.e. anything with cellulose. Ceiling tiles, gyproc, wood studs, natural-based carpet (wool or cotton), cardboard, wood panelling,etc. I know that's a long list and turning your basement into a plastic jungle isn't an option, but the combination of low humidity constant air movement and lack of food will eventually rid your basement of mouldy and musty smells.

In the meantime, a shot of diluted 1:1 bleach here and there in dark corners, on concrete, even on joists, studs and panelling just might lower the problem to acceptable standards. I found a 8"x8" cover on a anti-backup valve made of plywood to be the main culprit in the last house I did. This cover was sitting on a plywood box that literally stood in 1" of water for years. Cleaning that out and replacing the cover with a metal one did the trick...

Keeping the RH at 55% at temperatures around 18degC is "normal"; at lower temperatures, the %RH will go down, which is even better. On the other hand, if the temperature goes up to 21degC and the RH is still 55%, that's just on the borderline for growth, so something extra is needed.


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## orange (Feb 19, 2008)

Latest info on the RH and the house is that RH is now consistently about 47-49% and temp 20-22 C.


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## ccarlisle (Jul 2, 2008)

That's good! I understand the outdoor RH at 20 degrees (today) is around 55%, that means you should keep the dehumidifier going and the fans too, but keep the windows and doors shut...But now you're on top of the problem. 

But tell me do you smell mould down there?

I didn't mention all there is to it but I did mention the bleach mixture to kill off moulds (not necessarily mould spores) on many surfaces. This application will give a good kill ratio but the spores will still be in suspension in the air and ready to reproduce within the next 2 weeks, so there are further permanent steps to be taken if you have mould. 

What is the type of dehumidifier and what is its rating in terms of litres or pints per day? brand name?and what size area basement are we talking about here?


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## orange (Feb 19, 2008)

They have been running furnace fan and ceiling fans as well as dehumidifier since they encountered the problem. There is no mould smell at all and everything seems extremely dry and fresh. They did wash down walls, floor and shelves with a solution of javex. As you know we have had a lot of rain in Ottawa, but not nearly as much as we had continually in July when problem was noticed.

Whirlpool dehumidifier(I think 50 litres/day) They have it on shelf so it drains into laundry tub and drain.

House is 1700 sq ft bungalow.
We're talking full basement so it is about 1700 sq ft also.


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