single room heat recovery ventilation?/ air-air?

ahw23

Does anyone here have experience of through-the-wall heat recovery ventilation? And can anyone who has air-air ASHP tell me what impact, if any, it has had on humidity?
I have three reasons for asking. Firstly, we are still getting condensation upstairs after someone has a shower, even in May, despite all my efforts to encourage opening the bathroom window before wafting back into the house in a towel and a cloud of steam. Secondly, we have a garage that was converted into a utility room, extra bedroom and wetroom. The whole area is poorly insulated (which we're working on) and very cold, which means I can't currently even use the utility for drying clothes in wet weather (a bit of a pity as that's where the washing machine is and I'd rather not bring wet stuff into the main house, as we then get even more condensation there). Anyway, the old extractor fan for that bathroom has essentially fallen to pieces, so I'll be asking the electrician (coming tomorrow to look at some other jobs) about replacing it with a heat recovery model, such as the Expelair Solitaire. I'd be grateful for any reflections on these or alternatives before I do talk to him. The ASHP query is a much more speculative. I'm aware that you can't expect too much from them, they don't work brilliantly in winter and they're sub-optimal if you have a big gap between outdoor and indoor temperatures. However, I can't help wondering whether, in the long term, it might be worth having one running into this annexe, which is barely affected by any heating we have in the main house (e.g. the masonry stove we are planning on), and where most of the time we would just want to take the "edge" off the cold in autumn and spring, and keep the atmosphere dry. For what it's worth, we have 6.5kw PV E/W split, so some of the electricity would be self-generated (although given the panel positioning, very little on the "wrong" side of the equinoxes). Thanks!

silverwhistle

Hopefully Zeupater will be along soon to give you some input as he's fairly up on the subject.

Personally I've looked into MHRV for my bathroom as my girlfriend is capable and qualified to install it, and as I have solar panels and an immersion diverter and a wood burner in the lounge I rather like the thought of not wasting all the heat from my long, hot, post-footie baths!

ahw23

Thanks for replying, Silverwhistle! The electrician was very sceptical indeed, starting with some plain declarations that it wasn't a bathroom fan and couldn't be done. A few emails later, with links to product pages labelled "bathroom extractor fans", the firm had backed down to agreeing to fit, but still thinking we're idiots for not buying a cheap fan and running the towel rail more. From a purely money-saving point of view they may be right, but I don't care for the wastage, or for miserably shivering in a towel while a regular fan brings in sub-zero winter air.

Do you have any opinions on models? We're going to measure up tomorrow to see what fits, but it's probably between the Xpelair Solitaire (83% efficient, £297.989), the Kair KHRV150 (86% efficient, £285) or the Ventaxia Lo-Carbon Tempra P Heat Recovery Fan - 443312 ("up to" 78%, but just under £150). That's obviously not a full comparison, as it doesn't give the air-flow rates or electricity usage data. I'd be interested if anyone knows anything about these (including, of course, where to get them cheaper).

zeupater

ahw23 wrote: »

Thanks for replying, Silverwhistle! The electrician was very sceptical indeed, starting with some plain declarations that it wasn't a bathroom fan and couldn't be done. A few emails later, with links to product pages labelled "bathroom extractor fans", the firm had backed down to agreeing to fit, but still thinking we're idiots for not buying a cheap fan and running the towel rail more. From a purely money-saving point of view they may be right, but I don't care for the wastage, or for miserably shivering in a towel while a regular fan brings in sub-zero winter air.

Do you have any opinions on models? We're going to measure up tomorrow to see what fits, but it's probably between the Xpelair Solitaire (83% efficient, £297.989), the Kair KHRV150 (86% efficient, £285) or the Ventaxia Lo-Carbon Tempra P Heat Recovery Fan - 443312 ("up to" 78%, but just under £150). That's obviously not a full comparison, as it doesn't give the air-flow rates or electricity usage data. I'd be interested if anyone knows anything about these (including, of course, where to get them cheaper).

Hi

Previous discussion that 'Silverwhistle' mentioned (post & a couple after) here ... https://forums.moneysavingexpert.com/discussion/comment/70776772#Comment_70776772
... I've seen the unit since and it was a HR25. I'm told that it works well and has cured the condensation issues ....

Other options you have would include a dehumidifier or small portable air-conditioning unit with a dehumidify setting ... we've used both in the past for controlling humidity and you'd be surprised at how much water they 'scrub' from the air ....

On the Air to Air heat-pump remarks in the opening post ... in heating mode there'll be no effect on humidity as you need warm(er) air to pass over a cool(er) surface in order to cause moisture to condense. Having said that, some reversible units have the ability to schedule operation (mode & time) and have a specific (low airflow) dehumidification mode (ours does), so even in the cooler months you could schedule the unit to dehumidify for a while after a period of heating (for higher condensing efficiency) ... as for the worries on heat-pump performance, considering you already have PV, have a look at the thread referenced above from the very beginning and see whether it provides further food for thought on the suitability ....

HTH
Z

ahw23

Thanks! We have a dehumidifier (or rather two, if you count the one that's awaiting repair), but the OH gets grumpy about them eating the electricity.
The HR25 is apparently no longer made, the Kair model I mentioned needs a massive aperture, and so we were veering towards the vent axia, until we realised that the wall is too thin to take it, which explains why the wretched room is so cold to start with - it's only a half-brick thick. Now I'm back to (go)ogling insulation. I'll try to read through the whole thread soon.

Ben84

Drying clothes inside puts a lot of damp in to the house. If you can avoid that you don't need to try to capture or vent it later. I dry outside when the weather is good, but in the wet/cold weather I use a condenser dryer. It captures the moisture and vents the heat in to the house, so it contributes to space heating. Regular dryers send all the heat out the house - and suck heated air from the house out the wall with it, so that's bad all round for energy use. The condenser dryer is about the most practical and energy efficient option I've found so far. Heating with electric does cost more than gas, but we are getting to use the electric for drying clothes and heating the house.

I'm curious about the heat recovery ventilators, but not sure what kind of energy savings would be possible? I tend to turn the shower on, get wet, turn it off and soap, turn it on and rinse. It's on for a few minutes each time at most. Quite little water and energy use, and not that much steam going in to the air either when you do it this way.