I'm just looking for the quickest way to dry everything out - will be fixing all the issue causing the damp.
Drying out house - dehumidifier?
- Thread starter obliquegeek
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Open windows and lots of big fans to move the air about to get rid of large amounts of moisture, then close the windows and put in some dehumidifiers to finish the job.
Fans to move air about are about the cheapest way to get internal surfaces dry by increasing evaporation and then raising surface temperatures to that of the ambient air.
Ventilation to the outside is most useful when the outside air is coldest, and contains the lowest amounts of water. A full house change of air by opening all openings on a frosty morning can remove litres of water from the house - but you will also have lost all the heat.
Still, it is easier and cheaper to heat the remaining dry air than moist air.
Dehumidifiers are useless wastes of money in an occupied house where daily living tasks mean that humidity is being created and doors etc. are opened to other rooms and to the outside. Dehumidifiers remove moisture from the air, not the damp surfaces.
Ventilation to the outside is most useful when the outside air is coldest, and contains the lowest amounts of water. A full house change of air by opening all openings on a frosty morning can remove litres of water from the house - but you will also have lost all the heat.
Still, it is easier and cheaper to heat the remaining dry air than moist air.
Dehumidifiers are useless wastes of money in an occupied house where daily living tasks mean that humidity is being created and doors etc. are opened to other rooms and to the outside. Dehumidifiers remove moisture from the air, not the damp surfaces.
I appreciate that ventilation is key - but it's cold! If it was summer, I could simply open everything for a few months. But I can't, we still need to be able to live in it as comfortably as possible.
I've happy to shut some areas off (worst affect ones) and use a dehumidifier. Can't really ventilate them while at work - I'm not leaving windows open to an empty bungalow and there are no trickle vents on any of the windows in the house.
We're having new in-line extractors fitted to the bathroom and kitchen, vents in the soffits, clearing out the airbricks for the sub-floor ventilation, getting both chimneys checked. Any suggestion for anything else? anyway of adding a little more ventilation to the property that might help?
thanks for all the responses so far.
I've happy to shut some areas off (worst affect ones) and use a dehumidifier. Can't really ventilate them while at work - I'm not leaving windows open to an empty bungalow and there are no trickle vents on any of the windows in the house.
We're having new in-line extractors fitted to the bathroom and kitchen, vents in the soffits, clearing out the airbricks for the sub-floor ventilation, getting both chimneys checked. Any suggestion for anything else? anyway of adding a little more ventilation to the property that might help?
thanks for all the responses so far.
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Fitting extra ventilation is good for later.
For drying out excess moisture within the building fabric *now* you want to use dehumidifiers to their full effect, if you have dehumidifiers running then ventilation just means you are trying to dry more outside air.
For drying out excess moisture within the building fabric *now* you want to use dehumidifiers to their full effect, if you have dehumidifiers running then ventilation just means you are trying to dry more outside air.
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This is an interesting topic. Does anyone know more about how these work and dry the fabric?
The external humidity is say 80-100% on a cold wet winters day. The internal humidity is 80% (its damp inside due to water ingress). You fire up your dehum. Leave for 24 hrs. A few litres of water is extracted. I assume that some of this comes from the internal fabric and some from the air. The internal RH has dropped to say 60%. But how much water is from the air and the fabric? At what point is the extraction from the fabric optimal versus the extraction from the ambient air? When is the water from the fabric 'encouraged' the most to leave the fabric to enter the internal air space so can be extracted by your demum? Is the addition of heat (what ambient temperature) likely to speed up the process relative to the cost. Ie a humdifier will cost 2-300W per hour, but heating can cost 2-5kw in comparison.
The external humidity is say 80-100% on a cold wet winters day. The internal humidity is 80% (its damp inside due to water ingress). You fire up your dehum. Leave for 24 hrs. A few litres of water is extracted. I assume that some of this comes from the internal fabric and some from the air. The internal RH has dropped to say 60%. But how much water is from the air and the fabric? At what point is the extraction from the fabric optimal versus the extraction from the ambient air? When is the water from the fabric 'encouraged' the most to leave the fabric to enter the internal air space so can be extracted by your demum? Is the addition of heat (what ambient temperature) likely to speed up the process relative to the cost. Ie a humdifier will cost 2-300W per hour, but heating can cost 2-5kw in comparison.
Lot's of questions which I am too lazy to answer, but here are some points.
Humidity is relative to temperature, can't remember the exact relationship and you can probably find a graph on the net, so be careful when talking about outside and inside humidity. cold air with a 100% humidity will hold less moisture than warmer air with a lower % of humidity.
In terms of drying the fabric, moisture moves from objects to air if the air is drier, the drier the air the better, I am not aware of a logarithmic or exponential chart for this. Wood drying however is well understood and humidity has to be controlled carefully in kilns as to low a humidity results in too rapid drying. This would suggest that in most instances you will not run into diminishing returns in an air sealed space.
Cost is difficult to predict, because there are 2 types of dehumidifiers and lots of manufacturers variations of those.
Humidity is relative to temperature, can't remember the exact relationship and you can probably find a graph on the net, so be careful when talking about outside and inside humidity. cold air with a 100% humidity will hold less moisture than warmer air with a lower % of humidity.
In terms of drying the fabric, moisture moves from objects to air if the air is drier, the drier the air the better, I am not aware of a logarithmic or exponential chart for this. Wood drying however is well understood and humidity has to be controlled carefully in kilns as to low a humidity results in too rapid drying. This would suggest that in most instances you will not run into diminishing returns in an air sealed space.
Cost is difficult to predict, because there are 2 types of dehumidifiers and lots of manufacturers variations of those.
Jimbo320
As previous post, not an easy question to answer, to many variables.
Most of the Commercial Insurance Contractors undertaking drying out works so called Restoration Contractors generally these Contractors install fans, the intention is to move air past the damp / wet walls, the air movement at the surface of the wet plaster encourages the moisture in the Plaster to be evaporated and become suspended in the air, from there the De-Hums extract some of the now air-born moisture.
The Co-relationship between moisture in air, and its propensity to in effect drop out of suspension in the air and form moisture droplets that are at times visible
For more accurate and probably reliable info try Wikipedia and look for Wet and Dry bulb / Dew point. From here there are several other lines of enquiry that can be pursued?
Ken
As previous post, not an easy question to answer, to many variables.
Most of the Commercial Insurance Contractors undertaking drying out works so called Restoration Contractors generally these Contractors install fans, the intention is to move air past the damp / wet walls, the air movement at the surface of the wet plaster encourages the moisture in the Plaster to be evaporated and become suspended in the air, from there the De-Hums extract some of the now air-born moisture.
The Co-relationship between moisture in air, and its propensity to in effect drop out of suspension in the air and form moisture droplets that are at times visible
For more accurate and probably reliable info try Wikipedia and look for Wet and Dry bulb / Dew point. From here there are several other lines of enquiry that can be pursued?
Ken
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Thanks for the comments guys. The reason for the interest is the issue im having drying out a wall. Im not sure that there is no longer water ingress as the plaster is not drying out. It has been proably 3 weeks now. There was cracked render (since sealed 6 weeks ago) so the wall could well of been saturated previously. There is some condensation in the roof which could be dripping to the wall but it isnt that much. No obvious roof leaks or otherwise. There is also some black mould showing on the edge of a newly plasterboarded stud wall abutting the external wall that is not drying. I will see if i can get hold of a fan and place that in the room and point it at the wall next to the dehumidifer. All a bit puzzling, other parts of the room (not on external wall or its corners)can be seen to be drying out. External humidity is high (being in cornwall) and there is no heating as yet. I am getting a roofer round in new year to give a proper examination of the roof. Perhaps i can post a few pics if anyone is interested.
follow the wet bulb line and dew point etc to see the amount of water in the air at a given % and temp. RH and SH are the two types of humidity.
From the sound of it, the fabric of the wall will be well and truly damp. The drier you can get the air, the quicker moisture will be drawn out of the wall - but this will slow down as the depth through which the moisture needs to migrate increases.
So initially you might get "lots" of water out with the dehumidifier - but once you've dried the air and the surface of the wall (probably to plaster depth) you'll find the dehumidifier tank fills up much more slowly. All you can really do is "just let it get on with it".
Keeping the place nice and warm will help - it'll encourage evaporation from the wall, plus it'll make the dehumidifier work better (if it's the refrigeration type common for anything over the smallest sizes).
So initially you might get "lots" of water out with the dehumidifier - but once you've dried the air and the surface of the wall (probably to plaster depth) you'll find the dehumidifier tank fills up much more slowly. All you can really do is "just let it get on with it".
Keeping the place nice and warm will help - it'll encourage evaporation from the wall, plus it'll make the dehumidifier work better (if it's the refrigeration type common for anything over the smallest sizes).
Sure - I'm aware of that it's not to cure a problem - just to help dry things out quickly. Problems are being taken care of separately.
Currently got dehumidifier running in the worst affected room (door and windows shut) and it's consistently pulling out about 3 litres over a 24 hour period. Not 100% sure it's doing much to the room though, or where the water is actually coming from...
I'm leaning towards fixing the problems and as much ventilation as possible - seems to be the more reliable way.
Currently got dehumidifier running in the worst affected room (door and windows shut) and it's consistently pulling out about 3 litres over a 24 hour period. Not 100% sure it's doing much to the room though, or where the water is actually coming from...
I'm leaning towards fixing the problems and as much ventilation as possible - seems to be the more reliable way.
For it to work effectivly you need to make the room airtight, maybe tape windows, look at ceiling lightsockets (they can be draughty if poorly fitted).
Otherwise it will just keep sucking in humidity from the outside.
Otherwise it will just keep sucking in humidity from the outside.
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I bought one of these, very useful for checking the temperature of the dew points, min max temps.
Along with a laser thermeter, im able to check the parts of the wall that are below dew point.
Central heating going in so it should be interesting to see what happens once the wall temperature has risen.
Since the condensation in the roof issue looks like it has been improved considerably (if not fixed completely) noticeable improvements in drying out.
http://www.amazon.co.uk/gp/product/B000GFTH1M?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
Along with a laser thermeter, im able to check the parts of the wall that are below dew point.
Central heating going in so it should be interesting to see what happens once the wall temperature has risen.
Since the condensation in the roof issue looks like it has been improved considerably (if not fixed completely) noticeable improvements in drying out.
http://www.amazon.co.uk/gp/product/B000GFTH1M?psc=1&redirect=true&ref_=oh_aui_detailpage_o03_s00
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