Heat exchanger(s) for bathroom extractor fans

[Kneerly Down]

We have a few en-suite bathrooms that have normal extractor fans to vents on the roof and a few more bathrooms and en-suites that need ventilation added.
Instead of just sucking out the warm moist air to the outside I thought it'd much better to add one or more heat exchangers to pre-heat air coming into the house.
Has anyone experience of putting in such things or know good suppliers/makers?
Thanks

[Count Steer]

No great insight but I did do some delving a while ago and they go on an awful lot about air change rates being controlled as part of the overall installation. Also, particularly with bathrooms you need to deal with condensate - insulation of pipework so it doesn't condense to soon and dealing with the water + stopping it freezing at the drain.

Decided it was a far bigger job than I was prepared to do.

[Horse]

Might an alternative be to consider what air you're extracting?

- Vent over the shower, to extract the dampest air

- Install a matching 'in' fan so that you're not pulling warm air from the bedroom into the bathroom

[Mussels]

I've been looking at this for home, you want to look for MVHR systems. They seem pretty simple if you have room to run the ducting.

[Kneerly Down]

Thanks for the insights.
If we have a full complement then there'll be 7 bathroom extractors going in the main house and another 3 in the 'wings' so it seems like quite a lot of warmth to be just chucking out into the already damp highland air!

5 of the 7 bath/shower rooms are on the top floor and the other 2 on the middle floor, with plenty of room in the loft, plus there's an early 19th century equivalent of a maintenance duct that goes from the loft down to ceiling level in the kitchen on the ground floor but not sure if it's better to just duct warmed incoming air down to, say, the middle floor landing?

Thankfully there's easy access to the internal soil pipe for a condensation trap to feed into.

Just got our next delivery of heating oil ordered at 113ppl (probably plus 5% VAT) which is a bit of a shocker given the rate at which we go through the stuff!

[Kneerly Down]

No great insight but I did do some delving a while ago and they go on an awful lot about air change rates being controlled as part of the overall installation.

Do you mean controlled as in designing the dimensions right or controlled as in actively controlled once the system is installed?

[cheb]

I've a heat recovery system fitted in my house, it seems to work. Rega Ubblink IIRC, but I can confirm when I'm back home.

[Yorick]

Don't want to piss on your corner flakes.
But showers are 10/15 mins and once a day.
Need to factor that in.

[Kneerly Down]

Don't want to piss on your corner flakes.
But showers are 10/15 mins and once a day.
Need to factor that in.

Generally 2, sometimes 3 people using each shower (not necessarily at the same time!) so a bit more but ISWYM.
I had wondered about a heat exchanger for the shower and bath waste water but that's doing things I don't need. My main concern is getting the extraction vents in the shower and bathrooms and, if it's not too difficult, seeing as I'll be putting in new stuff anyway, adding in a HE to derive some benefit from the extracted air.

[Count Steer]

No great insight but I did do some delving a while ago and they go on an awful lot about air change rates being controlled as part of the overall installation.

Do you mean controlled as in designing the dimensions right or controlled as in actively controlled once the system is installed?

It's been a while but there was a lot about taking a 'whole house' view looking at air movement through the house, eliminating draughts/uncontrolled air ingress/escape and then designing/sizing everything and controlling the system to achieve the desired air changes per hour. (Noise was an issue to address too as was filtration iirc).

I decided that an ad hoc upgrade/retrofit approach wouldn't work and the whole thing was too much bother. I thought it was going to be simple. It was like the classic 'if I were you, I wouldn't start from here' directions. I thought I could start simple and add on but nothing seemed to support anything but the 'whole house' approach.

[Mussels]

Yes, it works best on a sealed building so if it's drafty it won't make much difference.
A big selling point for me is the air coming back in is dryer, so much so that it can cause problems but I don't imagine that happens in the UK. My house is pretty well sealed so a good candidate.

If energy saving was my only goal then it probably wouldn't be worth the cost, even more so for those wall units that are supposed to recover heat from just the wall vent.

[Count Steer]

Yes, it works best on a sealed building so if it's drafty it won't make much difference.
A big selling point for me is the air coming back in is dryer, so much so that it can cause problems but I don't imagine that happens in the UK. My house is pretty well sealed so a good candidate.

If energy saving was my only goal then it probably wouldn't be worth the cost, even more so for those wall units that are supposed to recover heat from just the wall vent.

Previous house was designed around a warm air system (nowhere to put radiators) and that, originally had an integrated humidifier because of potential dry air issues. Then, apparently after Legionnaires outbreaks made the news, the humidifier was decommissioned. Good system though....good in hot weather for keeping the place fresh too, just push the air around.

[Kneerly Down]

Yes, it works best on a sealed building so if it's drafty it won't make much difference.

So a listed 18th century building with single glazing and doors with interesting angles, next to the sea in NW Scotland might not be ideal?

Main issue is getting rid of humid air from the bathrooms.
Can't ever imagine the air in our house being too dry!
A bonus would be recovering some of the heat that is being pushed out of the house. Even better if some of that slightly warmed air replaces completely cold air that would otherwise be coming in through the various gaps round doors, windows, fireplaces, etc!

[Mussels]

As a money saving idea it won't work for you but as you need a ventilation system anyway it may be ok.
The heat exchanger itself will be a few hundred quid, take up space somewhere indoors, need servicing and not save you much money.
Then you find it fails because people leaving doors open or closed messes up the air flow, this is a sticking point for me as I want to ventilate bedrooms but that doesn't work well at night when the doors are closed.

I really like the idea but it doesn't stand up to scrutiny unless you let the system dictate how you live. For now I've adjusted the humidistat in the bathroom and I'll look at this again in a few months when there's better info available.

[demographic]

The areas where you gain from having a good air handling unit over a noisy old extractor is that it gets used more, you're far less likely to disable them because of the noise they make and then that transfers to a drier building thats less likely to get dry rot (most common rooms for that to start are in the ceiling above the kitchenand bathrooms).

People want to be warm while they shower and if a windows open when its cold out they generally close it, then you get condensation which leads to damp.


D9ne right and they make a massive difference, doing it wrong is just a waste of time and money.