Sat, 16 May 2026 05:03:09 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7584#Comment_7584 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7584#Comment_7584 Thu, 04 Oct 2007 22:14:43 +0100 dancing_sam I am interested in replacing our current “hole in the wall” ventilation in our bathroom with a ‘single room heat recovery ventilator’ - the type that would just fit through the wall, using the current hole, with little modification. I am wondering if anyone has any experience of these? I have only found one supplier that seems to be doing them for about £250, which seems quite pricy. Can anyone recommend any other suppliers/ types?

I also had a thought that I might be able to run this off a fairly small and simple 12V solar charged battery (the bathroom is upstairs and the bat could sit above in the loft)? Any advice on either fronts most welcome. Thanks,
Samantha]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7586#Comment_7586 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7586#Comment_7586 Thu, 04 Oct 2007 23:03:06 +0100 tony
12v fans are easy to come by

You could make you own heat recovery system with a wooden box a plastic tray and some cling film and two fans.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7592#Comment_7592 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7592#Comment_7592 Fri, 05 Oct 2007 09:40:32 +0100 dancing_sam https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7604#Comment_7604 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7604#Comment_7604 Fri, 05 Oct 2007 13:08:14 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7614#Comment_7614 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7614#Comment_7614 Fri, 05 Oct 2007 17:09:00 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7658#Comment_7658 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7658#Comment_7658 Sat, 06 Oct 2007 20:03:17 +0100 dancing_sam Though it is expensive, I am still edging towards getting one. It seems a tad annoying to goto a lot of effort to get cavity wall insulation, draught proof, and double glaze (as we have done), and then pump the heat out in an uncontrolled fashion from out upstairs bathroom.
Is there anyone here that has used these single room units?
Thanks.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7665#Comment_7665 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7665#Comment_7665 Sat, 06 Oct 2007 22:36:00 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7691#Comment_7691 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7691#Comment_7691 Mon, 08 Oct 2007 12:18:47 +0100 Mike (Up North)
Havent used one (yet), but have a look at Kair/Kiltox KHRV150 eco and Vent Axia HR25. You are right they are pricey. But the vent axia was much less than the Kair. Check the volume flowrates though as they are not that great, particularly if you have to shift x lit/min or so-many room volumes from a bathroom/utility room to meet regulations.

Cheers]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7751#Comment_7751 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7751#Comment_7751 Tue, 09 Oct 2007 17:17:06 +0100 ken davis https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7764#Comment_7764 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7764#Comment_7764 Tue, 09 Oct 2007 20:43:12 +0100 chuckey Frank]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7841#Comment_7841 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7841#Comment_7841 Thu, 11 Oct 2007 21:19:04 +0100 dancing_sam
Thoughts so far on the three I have looked at (am i missing any others?):

The Silavent Energex -
Price: £70 – but need to check – I think this is the single speed version, and the dual speed could be quite a bit more pricy?
Motor: 12V AC.
Extraction rates: Low 22m³/h
High 70m³/h
Power consumption: Low 15W
High 40W
dBA 15 - 35
Input: 240V AC or 12V AC S.E.L.V.
Notes: Seems to be the cheapest, though I still need to track down a supplier and check. Website does not provide very good data to compare the efficiency of the heat exchanger. Sounds like the humidity controller does not work well and is not adjustable.
Link: http://www.silavent.co.uk/products/heat_recovery/energex-technical.asp


Kair Heat Recovery Ventilator
Price: £330
Motor: 12V AC
Extraction rates: Low 19m³/h
High 38m³/h
Power consumption: Low 9W
High 46W
dBA 21 - 45
Input: 240V AC which is transformed down to 12V AC in the separate humidistat control box.
Notes: The most expensive – though it seems like a good idea to have a separate/remote humidistat/control, so it is not measuring the humidity right next to the extractor fan (incoming and outgoing air).
Link: http://www.kiltox.co.uk/products/hrv.htm



Vent-axia HR25
Price: £227
Motor: 24V DC
Extraction rates: Low 15.7m³/h
High 54.6m³/h
Power consumption: Low 1.9W
High 24.1W
dBA 17 - 49
Input: 240V AC and possibly 24V DC
Notes: Seems to be the most power efficient, and hopefully will take a 24V DC battery input (am enquiring now). Middle price (though still expensive). Humidity control is adjustable, and can override with manual control (I think – can anyone confirm?). Might be the best option for us as we are keen on powering it with solar – would be no loss of energy from any step down transforming or inverters.
Link: http://www.vent-axia.com/products/vacas/hr25.asp]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7861#Comment_7861 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7861#Comment_7861 Fri, 12 Oct 2007 18:54:52 +0100 chuckey Frank]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7918#Comment_7918 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7918#Comment_7918 Sun, 14 Oct 2007 11:25:51 +0100 ted https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7959#Comment_7959 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7959#Comment_7959 Mon, 15 Oct 2007 16:29:36 +0100 dancing_sam cost us electricity doing it? It does say it comes with a weather cowl - but is this effective? I would hope that on a device of this price this wouldn’t be a problem, but can anyone here make me less nervous about this?

Many thanks,
Bongo.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7971#Comment_7971 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=7971#Comment_7971 Mon, 15 Oct 2007 19:02:48 +0100 ted https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11389#Comment_11389 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11389#Comment_11389 Tue, 25 Dec 2007 16:47:21 +0000 Sid_Kumar https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11394#Comment_11394 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11394#Comment_11394 Wed, 26 Dec 2007 11:16:48 +0000 chuckey What I suspect is that the 86% recovery is at a very modest temperature differential, in to out of say 5 degs. When the differential increases above this, because of the thermal resistance of the plastic heat exchanger and its limited size, the hot air can't transfer its heat to the incoming (cold) air at one end and at the other end the cold air can't pick up heat from the exausted (hot) air. Its a shame that the efficiiency is not stated at a working temperature diffential of some thing that is relevant, say a internal 20 deg, external zero deg C, or 20 deg C. This also catches any potential icing problems.
One other point is that the water content in the air carries an appreciable amount of heat energy, so cooling wet air releases more "heat" then cooling dry air. This added heat due to the water content is called latent heat. The heat in the air alone is called sensible heat. So a good spec would quote sensible heat recovery and latent heat recovery. Think of the moisture content of the shower room air!
Frank]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11406#Comment_11406 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11406#Comment_11406 Wed, 26 Dec 2007 22:25:09 +0000 EasyBuilder https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11407#Comment_11407 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11407#Comment_11407 Wed, 26 Dec 2007 23:46:47 +0000 passivhausfan
Have a look at: http://en.wikipedia.org/wiki/Countercurrent_exchange

I suspect the 86% figure might have something to do with latent heat? Not sure, though. Maybe they just pulled it out of the air.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11415#Comment_11415 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11415#Comment_11415 Thu, 27 Dec 2007 13:33:42 +0000 EasyBuilder
Counterflow heat exchange looks promising. I see that the Xpelair Xcell range of heat recovery units use a counterflow heat exchanger and claim up to 92% efficiency.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11418#Comment_11418 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11418#Comment_11418 Thu, 27 Dec 2007 14:56:38 +0000 chuckey I would have thought that the unit could be represented by a "perfect" heat exchanger with a lossy heat path bypassing it, like a bit of none heat insulator ( solid bar of metal). The lossy bit will have a loss directly proportional to temperature. I see the problem with the "perfect" heat exchanger, at the units higher speeds a lot of the air will not touch the sides of the heat exchanger medium and so will go whistling through carrying its heat with it. Or conversley will come in like a jet engine and not pick any heat up!
Frank]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11447#Comment_11447 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=11447#Comment_11447 Fri, 28 Dec 2007 00:33:17 +0000 EasyBuilder http://www.applied-energy.com/clientfiles/File/Brochure%20PDFs%202006-07/XP-home_systems.pdf for details. On page 55 there are performance charts showing how efficiency varies with air flow, just as you expected.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=68688#Comment_68688 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=68688#Comment_68688 Fri, 11 Dec 2009 10:58:22 +0000 timbrennan https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=68694#Comment_68694 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=68694#Comment_68694 Fri, 11 Dec 2009 11:36:12 +0000 mrswhitecat
The other bathrooms have 'normal' Ventaxia showerlight extractors. I was worried about the wind thing (plus expense), so I've hedged.

Unfortunately I can't tell you yet how well it works as the house isn't finished yet.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=68974#Comment_68974 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=68974#Comment_68974 Sun, 13 Dec 2009 23:50:45 +0000 Paul in Montreal Posted By: timbrennanPerhaps the main purpose of bathroom ventilation is to remove moisture in the air.There's other toxic gases which sometimes need removing from bathrooms ;)

Paul in Montreal.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=70647#Comment_70647 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=70647#Comment_70647 Sun, 03 Jan 2010 15:08:36 +0000 suegreenbuilding
In winter I dry the washing over the bath and open the window (but close the bathroom door) during a day when I don't have the heating on and preferably one when it isn't raining outside. However, there will be a lot of heat loss through the window.

Mechanical ventilation and heat recovery sounds like a good solution but I suspect that the carbon cost would outweigh the benefits (i.e. carbon associated with energy used would be greater than energy associated with the heat lost through opening the window, on basis of gas CH system). Maybe on the basis of installing a PV system the equation would be positive? (But expensive).]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=238555#Comment_238555 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=238555#Comment_238555 Tue, 05 Apr 2016 16:31:06 +0100 Rick_M https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=238630#Comment_238630 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=238630#Comment_238630 Thu, 07 Apr 2016 02:31:29 +0100 wookey Envirovent Heatsava:
http://www.envirovent.com/specifier/products/single-room-heat-recovery/heatsava/
Trickle: 4.9W, 6.5l/s, 22dBA (100mm hole model)
Boost: 20W, 13 l/s, 39dBA (100mm hole moel)
Automatic summer bypass mode
Auto frost protection
Humidistat auto boost
up to 75% heat recovery
100mm or 150mm hole
Can be installed from inside only
Removable cleanable heat exchanger
Wireless option
IPX4
£318 (100mm)
£377 (150mm)


Vent-Axia Lo-carbon Tempra:
http://www.vent-axia.com/range/lo-carbon-tempra.html
3.2W min
6,9,15 l/s speeds
up to 78% heat recovery
Manual summer bypass mode
IPX4
100mm hole
SELV or mains
£182 (mains pullcord) -£365 (SELV humidistat+timer)

HRU-Wall
http://www.justfans.co.uk/heat-recovery-inside-wall-hru-wall-p-1167.html
100mm and 150mm versions
'Up to 90% efficient'
Swaps direction every 70s
£238 (100mm)
£313 (150mm)


The heat-sava seems like a nice design.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=238631#Comment_238631 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=721&Focus=238631#Comment_238631 Thu, 07 Apr 2016 08:58:08 +0100 yclairejenkins