Green Building Forum - SolarVenti dehumidifier with positive ventilation - opinions?

SolarVenti dehumidifier with positive ventilation - opinions?

JackyR — Tue, 02 Dec 2008 13:15:21 +0000

I'm quite taken by this gadget: http://www.solarventi.co.uk/

As Peter Clark said elsewhere:

Posted By: Peter ClarkA PV panel on a south facing wall together with an air intake and heating panel. Blows hot, dry (you hope) air into the room behind. A kind of positive ventilation but no leccy for the fan. Won't work on a winters day that is overcast, but overall throughout the season, may make a significant difference. The larger ones they are claimimg significant space heating effect also.

What do we all think?

SolarVenti dehumidifier with positive ventilation - opinions?

JackyR — Tue, 02 Dec 2008 13:18:18 +0000

Here's that link again, clickable: http://www.solarventi.co.uk/

SolarVenti dehumidifier with positive ventilation - opinions?

Peter Clark — Tue, 02 Dec 2008 13:27:42 +0000

I wonder why it cannot charge a battery as well, and then have some spare juce for when the sun is gone but ventilation is needed?

SolarVenti dehumidifier with positive ventilation - opinions?

JackyR — Tue, 02 Dec 2008 13:27:50 +0000

First thought: it relies on outdoor air having lower absolute moisture content than indoor air.

Is this generally true in the UK (famed for its soggy snow instead of crisp powder)? Or do we sometimes have equal moisture content in and out, but different relative humidities?

SolarVenti dehumidifier with positive ventilation - opinions?

Peter Clark — Tue, 02 Dec 2008 13:45:41 +0000

Posted By: JackyRFirst thought: it relies on outdoor air having lower absolute moisture content than indoor air.

Is this generally true in the UK (famed for its soggy snow instead of crisp powder)? Or do we sometimes have equal moisture content in and out, but different relative humidities?

Generally, I think, the air in England is likely to average RH well above 50%.

I think the blurb is that in winter (when you will want to use it) and when the sun is shining, it is likely that the external air is less humid.

SolarVenti dehumidifier with positive ventilation - opinions?

Ed Davies — Tue, 02 Dec 2008 15:31:55 +0000

I can't see any reason why indoor absolute humidity would ever be lower than outdoor except with air conditioning or when the outdoor content has just risen and the indoor environment (including walls, etc) hasn't caught up. After all, processes inside houses which are not, long term, in balance for humidity tend to emit it rather than absorb it.

Perhaps the controller on a Solarventi-like thing could to take the actual humidities into account, as well as the temperature, to work better here.

SolarVenti dehumidifier with positive ventilation - opinions?

Peter Clark — Tue, 02 Dec 2008 15:58:11 +0000

Is it not true that all ventilation technologies involve getting external air, and its humidity, inside, or is it possible to dehumidify the air with some MVHR systems?

In any case, in the winter, when the air is colder, it is likely to be less humid naturally because of the temperature?

That seems to be the strategy with solarventi, take advantage of naturally lower humidity in cold air, but heat it up just before injecting it into the house.

I wonder how effective it would be over a season. Clearly there will be many days, or groups of days with no sun, at least where I live in the North East.

Peter

SolarVenti dehumidifier with positive ventilation - opinions?

chuckey — Tue, 02 Dec 2008 17:57:17 +0000

Roughly speaking, heating any outdoor air at below 9 deg C, will get you a comfortable indoor humidity of < 60% at > 16 Deg C. If you want a more accurate calculation, look at a Psychrometric chart. It details how much water vapour(gm) there is in a kg of dry air at various temperatures with the relative humidities shown.
Frank

SolarVenti dehumidifier with positive ventilation - opinions?

taichi — Sat, 14 Feb 2009 11:05:48 +0000

Thought I might put a bit more meat on the bone as far as my Solarventi is concerned. I am so impressed that I have decided to become an agent for the company. I already run a humidity related company but that is in the catering and hospitality refrigeration industry. But that to one side, I have been very impressd with the PV panel, which has the ability to both warm and pump air into and through the house. I can also control the way the solar energy is used by regulating the flow. Less air = more heat or greater air flow whichever is required at the time.
If you want more information on the Solarventi system you can call Chris on 07515560594 and he will talk you through it.

SolarVenti dehumidifier with positive ventilation - opinions?

Suz — Tue, 19 May 2009 00:03:43 +0100

Ive got one fitted to my part time cottage. Pros: very helpful company, have thought through the fitting, does seem to keep the place ventilated. Cons: I'm not too convinced about the 'dry air' sell, for reasons as above; they have used a very noisy fan, the noise is really quite intrusive. Some work on sourcing quiet fans would be a good idea. But the general functioning is an impressive demonstration of solar generated 'lectric.

SolarVenti dehumidifier with positive ventilation - opinions?

CWatters — Tue, 19 May 2009 14:03:54 +0100

Posted By: Peter ClarkIs it not true that all ventilation technologies involve getting external air, and its humidity, inside, or is it possible to dehumidify the air with some MVHR systems?

My understanding is that normally it's less humid outside than in. If it's not then you need air conditioning to do anything about it.

SolarVenti dehumidifier with positive ventilation - opinions?

Peter Clark — Tue, 19 May 2009 15:26:36 +0100

Posted By: CWatters
Posted By: Peter ClarkIs it not true that all ventilation technologies involve getting external air, and its humidity, inside, or is it possible to dehumidify the air with some MVHR systems?

My understanding is that normally it's less humid outside than in. If it's not then you need air conditioning to do anything about it.

I think I may be confusing relative and absolute humidity.

If it is warmer outside, then it will soon be warner inside and the RH will be the same in and out, is that right?

But if it is colder outside, the external RH will be higher probably, but when that cold air is heated up inside, the RH will be lower.

I don't know what that means about the solar-Venti, I have heard that the fan is a bit noisy 'tho.

SolarVenti dehumidifier with positive ventilation - opinions?

trule — Tue, 19 May 2009 16:38:14 +0100

I wonder if you could build one yourself for less money? There does not seem to be much to it.