Any advice on heat recovery fans from Vent Axia and how good thier "h" humidity function works?

diy_massacre · Jun 27, 2021

Hi

I have an old house which has had double glazing fitted to the rear of the property, in the kitchen, good for heat retention but not for damp. I was expecting to buy a Vent axia in-room MHVR fan to help with drying out the room and maintaining its temperature.

The model which I think continuously runs 24/7 but can also detect higher humidity so when there is alot of cooking/boiling and humidity rises it ramps up its output. Has anybody had any experience if these work well or not?

Thanks

diy_m

diy_massacre · Jun 30, 2021

Ric2013 said:
Crossed wires here. It will monitor the air inside the room. However, the air in the room will be replaced with outside air which may have a high RH. So the 'new' air in the room may also seem damp to the sensor. The fact that your fan will preheat the incoming air will certainly help it distinguish, however, the very act of heating the air will cause the RH to fall somewhat.

Hi Ric2013

Yes understand your point, thanks for the clarification. Think I will get one anyway even if it overruns sometimes.

Many thanks

diy_m

gmartine · Jul 1, 2021

hometech said:
I don't expect the average person to understand so no point in discussing that with you

Murdoch said:
Back with your condescending replies again?

Ric2013 said:
It depends what percentage of heat is recovered and if you need constant operation. If the fan consumes 5W of electricity and is run constantly, that's 0.13kW per day.

But 9l/s is 32cu m. an hour. So you could be changing all the air in the room once per hour at that rate.

As far as I can gather (very roughly indeed), it takes around 1.2W to heat a cubic meter of air by 1°C. So at 20°C indoors and 10°C outdoors, every day would have 770 cu m x delta 10 x 1.2W = 9.2kWh. Recover half that energy and you've saved 4.5kW. Nearly a pound's worth of electricity if you're a low energy user or on a genuinely green tariff.

So, assuming the fan lasts only 3 years, and assuming a 100 day heating season it is still paying for itself compared with just opening the window. So not a stupid idea at all.

I have no problem with the principle of heat recovery just the thought of using an extractor fan designed for a high humidity environment like a bathroom being used in a room that it isn't designed for. The issue is the hex's on these particular fans are usually triggered by humidistat that can be set but not at a level that is applicable for say bedrooms as is being preposed not to mention the noise emanating from them also makes them inappropriate.