Solar Air Heating Dehumidifiers

[tenniswitch]

A friend recently read an article about a man who keeps his holiday home dry using one of the SolarVenti brand solar-powered dehumidifiers.  This is interesting to me as we are required to turn off our electricity during the months that we aren't in residence.

Has anyone had experience of using those or any other similar product in an old house?

(I'm not trying to advertise, just to eliminate some mustiness, especially in an understairs closet.)

[Clair]

I looked into this a while back... no experience though...

These are the pages I bookmarked at the time:

http://www.duquai.fr/FR/zonnepanelen-prijzen.html

http://www.rayon-solaire.com/ventilateur.htm

http://www.grainsdsoleil.com/index.php?art=7&th=324

[tenniswitch]

Thanks, Clair, I'll take a look at those links.

[Gluestick]

I looked at the OP's link and whilst it seems an innovative idea, I would have one concern.

It appears to be a "Green" version of an earlier system, where an electrically powered fan heater simply pumped in heat; which raised the dewpoint.

I could see no ventilation exit to outside; nor any mention of this on the site.

Problem is with old French houses there is no membrane beneath the floor tiling (Which in very old places can be a flagged floor, laid simply on beaten earth) and no DPC (Damp Course at the bottom of the walls). Both of which allow the natural water table to encourage moisture to creep in.

Our place was originally 200 years old: much re-built circa 42 years ago by the previous - French - owner: with the absence of a membrane and DPC.

The first and perhaps most critical thing was to promote free air circulating, by way of cross ventilation: thus I installed closeable vents where necessary: and we leave doors open to promote cross-ventilation. This made a major difference within months.

The next step was to purchase and use a proper de-humidifier: i.e. a fridge pump based professional unit, which has the benefit of a "Constant Drain" facility (i.e. it can be connected to a waste pipe and dumps captured water outside or wherever you want it to exhaust) and an automatic hygrometer switch (Humidistat).

What convinced me of the need for the de-humidifier were two realities: in Winter once enough heat had been pumped into the house and more critically the fabric of the house, then pools of water collected on the tiled floor! Mainly under beds, furniture etc. Next was Spring: open up the house; open windows; inject modest levels of necessary heating (e.g. woodburner in the evenings) and et voila ! The floors would quickly mist up with condensation!

Most ventilation fans tend to be fitted at the top of rooms. One problem here is that since hot air rises, then such fans tend to extract heat, which exacerbates the core problem.

One school of thought suggests that since damp air is lighter than dry air, then the damp air will rise: however the humidity in most enclosed space tends to be even, top to bottom of the space.

It might be an idea to consider a VMC: one of the better systems which capture heat rather than dump this to outside.

A VMC plus heat: a constant "Drip Feed" of heat into a closed-up unoccupied property is essential to prevent the growth of the moulds which cause "Mustiness" and fungal attack.

It is not an easy proposition in older properties when security is taken into account, I've found.

Bonne Courage !

[BIG MAC]

Interested in Gluestick's water under furniture observations as we have similar problems and also looking for a passive method of dealing with it if possible.

[Gluestick]

A Mop and Bucket thus far seems the best passive solution, Mac!

Trouble is the more heat one adds (Thus raising the dewpoint) the greater the saturation of the air; and without UF heating, the whole floor mass (Concrete plus old synthetic marble tiles), acts as a giant condensor.

When this first happened, I thought it was a case of massive rising damp from the floor! ( The house is built on a significantly sloping plot, to the point where, at the front aspect, we have a robust retaining wall, between the house and the road. And the water table is quite high: to the level where a new house being planned just along the road was refused point blank persmission of a Cave, unless the owners could provide some seriously expensive ground works and full tanking, which proved too expensive for their wallet.

However my fears were groundless: there is no greater rising damp than any other similar property: and I later doscivered it is quite common in these old places.

C'est la vie !

Humans breathing and cooking and showering and washing etc, simply exacerbates the problem.

When I add up heating costs and consider this humidity problem, I've often wondered whether I would have been better off as a Polar Bear!

[:)]

[BIG MAC]

The floor which causes us problems is like ancient quarry tiles on beaten earth. I am thinking of ripping it up and putting down an insulated screed.

[Gluestick]

Then don't forget to keep and sell the flags, Mac: worth serious dosh to architectural recyclers.

And if your are going down that route, do consider UF heating: it is the ultimate solution, I believe.

As I stated previously, my inescapable conclusion is that since warm air rises and colder air falls (Natural Thermocycle), then as the moisture-laden air hits the floor, this acts as a very effective (But unwanted) condensor: hence the pools of water.

Even a modest electric UF system would cure the problem, IMHO.

I don't really want to rip up 150 Sq.M of this!

[IMG]http://i74.photobucket.com/albums/i278/Michaeleff/FelthamsHouse005.jpg[/IMG]

 

[tenniswitch]

Looks as if you've more than a nodding acquaintance with architectural recyclers, Gs.  Nice detailing. [:)]

[Gluestick]

Love 'em!

Presently haunting farmer's old barns for more old beams..........