Anyone have experience with MVHR units in older properties?

[flowera]

Our Victorian brick detached house suffers from excessive condensation in winter and could also do with some extra heating upstairs. We don't yet have any extractor fans in the bathrooms. In winter we light three wood burners downstairs which do a fantastic job of keeping downstairs very warm, but very little of that heat makes it upstairs. We rely on radiators to provide additional heating but, because we have an expensive to run oil boiler we try to minimise use of those.

I've been thinking about installing a MVHR system in the loft to extract moisture-laden air out of the upstairs rooms and to also pull hot air up from downstairs and to use it heat fresh air that will then be pumped in to the upstairs bedrooms. The link below is a typical unit I'm considering:

http://www.xpelair.co.uk/xcell-350v-ec-bp-mechanical-ventilation-units-with-heat-recovery-and-summer-bypass-for-larger-dwellings.html

Has anyone installed such a system in an older property and have any positive/negative experiences to share? It is going to be quite expensive to acquire and fit so I don't want to waste money on something that won't give much benefit.

Alan.

 

[Pford75]

I haven't used one of these, but I'm surprised your upstairs rooms are the coldest. In our house, a combination of decent loft insulation and poor underfloor insulation means that most heat travels from the ground floor to the first and second floors quite quickly. It then stays there. The problem is exacerbated by a very large open stairwell which acts as a kind of heat tunnel for all the downstairs warmth

 

[AMc]

They installed one in the house on the BBC series "It's not easy being green" in combination with woodburners and no central heating. The series was variable in terms of its clarity and its green credentials but I suspect that had more to do with TV production than an inherent lack of understanding from Dick Strawbridge himself.
http://www.newhousefarm.tv/

I would also have a search around on The Green Building Forum for more on MVHR
http://www.greenbuildingforum.co.uk/newforum/?CategoryID=4

 

[88v8]

'In winter an automatic defrost cycle prevents freezing of the condensation removed from the dwelling.' it quoth. So is this a glorified heat pump?
The 'defrost cycle' presumably means that when it gets cold, as I believe it might do some winters, it will use heat keeping itself from freezing up. I'd want to see the performance in cold weather, all very well quoting averages.
And is it really quiet enough to sit in the attic?

Ducting.... looks more suitable to a new build than a retro-fit.

Bear in mind also that if you suck air out of the rooms with the woodburners, you'll have to provide a correspondingly greater air inlet to those rooms - the woodburners need air too :shock:

I bet if you invested the capital this will eat up, it would produce enough income to run your oil boiler, and you'd still have the capital

Ivor

 

[Penners]

I haven't used one of these, but I'm surprised your upstairs rooms are the coldest. In our house, a combination of decent loft insulation and poor underfloor insulation means that most heat travels from the ground floor to the first and second floors quite quickly. It then stays there. The problem is exacerbated by a very large open stairwell which acts as a kind of heat tunnel for all the downstairs warmth

Like Pford, I'm very surprised that your upstairs rooms remain cold while you have three woodburners roaring away downstairs. Our own winter experience is quite different.

Our cottage has a woodburner fitted in the sitting room. Like you, we try to avoid running the oil-fired heating for any longer than necessary, so in cold weather we keep the woodburner going all day. I'm not going to claim that this keeps the entire house toasty, but we do find that leaving doors open allows the heat to percolate through the house, including upstairs, and take the chill off most of the rooms. I should add that, although our Georgian cottage has solid brick walls, we do have very generous loft insulation.

If you're running three woodburners, then I'd be surprised if you can't allow a fair bit of heat to waft upstairs. Then you need to take steps to trap it there.

Speaking for myself, rather than spending a lot of money on a high tech solution, I'd rather spend a modest amount on this low tech approach:

 

[Onetap]

'In winter an automatic defrost cycle prevents freezing of the condensation removed from the dwelling.' it quoth. So is this a glorified heat pump?
The 'defrost cycle' presumably means that when it gets cold, as I believe it might do some winters, it will use heat keeping itself from freezing up. I'd want to see the performance in cold weather, all very well quoting averages.
Ivor

No, it's a cross-flow plate heat exchanger, a stack of plates with gaps between them, so a big heat exchange area. Extracted air and incoming air pass through alternate gaps, exhanging heat. If the incoming air is cold, moisture in the extract air will condense and can freeze.

93% efficiency is mentioned, which is odd; I'm fairly certain 50% is the theoretical maximum.

I wouldn't bother with one of these in a Victorian house, unless every other insulation and draught proofing measure had already been fitted. 3 wood burners? Stoves or open hearth?

 

[flowera]

'In winter an automatic defrost cycle prevents freezing of the condensation removed from the dwelling.' it quoth. So is this a glorified heat pump?
The 'defrost cycle' presumably means that when it gets cold, as I believe it might do some winters, it will use heat keeping itself from freezing up. I'd want to see the performance in cold weather, all very well quoting averages.
Ivor

No, it's a cross-flow plate heat exchanger, a stack of plates with gaps between them, so a big heat exchange area. Extracted air and incoming air pass through alternate gaps, exhanging heat. If the incoming air is cold, moisture in the extract air will condense and can freeze.

93% efficiency is mentioned, which is odd; I'm fairly certain 50% is the theoretical maximum.

I wouldn't bother with one of these in a Victorian house, unless every other insulation and draught proofing measure had already been fitted. 3 wood burners? Stoves or open hearth?

The wood burners are stoves. The house is typically 'leaky' so my major concern is how effective MVHR would be... seems to be quite some doubt that it is going to be worthwhile... had wondered if anyone here had fitted one to an older property with some success?

The loft is well insulated, but wonder if I might simply add stand-alone humidistat extractors to each bathroom and simply not bother with any attempt to use heat exchangers???

 

[Penners]

The house is typically 'leaky'

Well, if I might suggest, there's the place to start. Try to reduce the heat leakage from the house, and you should help to conserve whatever heat your generate. Your thoughts on humidistat extractors in bathrooms seem sound to me.

 

[AMc]

These systems are a key component of passivhaus low energy new builds so in the right circumstances they certainly work.

As a first step draught proofing will certainly improve your heating bills. IMHO planned ventilation will help your damp issues too but you'd be crazy to do the second without the first. If you don't channel all the air exchange through the unit then you will lose heat.

Your best bet with the MVHR unit is to ask a few installers to look at the house and provide quotes. Also ask them for customer references for similar properties. If they can't/won't do that then you can draw your own conclusions about suitability of the systems and installers.