Buying a house with a heat recovery ventilation system.

[dhutch]

If you where looking to buy a house with a MVHR system installed would it increase the attraction of the property, reduce the attraction, or not effect it?
Making the assumption that job had been done competently, and that house was otherwise a normal build and in the condition you would expect.

I would be very interested in your thoughts.


Daniel

 

[AronSearle]

and that house was otherwise a normal build

Not sure what you mean by that.

For it to work properly it has to be built better than what most builders have done for years.



But anyway, No I wouldn't want it, don't think you need it for the UK climate. Rather just have a well built modern house with good insulation installed properly (wrap around, and not the usual gaps of insulation at the eaves).

It's what we are starting to do now and other countries have been doing to 30 odd years.

 

[dhutch]

Not sure what you mean by that.

Well, hard to say what is normal, but I just mean a fairly regular brick uk build, say 1940-1980's, with retro fitted loft insulation, cavity wall filling, and double glazing throughout, suspended woodern floor with draft membraine, no trickle vents or air bricks.
Ie, well inslulated with some retrospective thought towards air tightness, but not modern or 'eco' build.

 

[AronSearle]

I would be a bit dubious of such a system in such a poorly built house.

From what other people have said, MVHR is not that great at generating heat, so really needs a well insulated building to shine (and shine it can).

The insulation levels in what you have described will be so poor (in context) you would need normal heating anyway, the airtightness might have been achieved, but I wouldn't bet money on it, builders seem to struggle with new builds designed a bit better, let alone retrofits.

I think realistically you need to be looking at insulated render being applied to start getting the required U-values.

suspended woodern floor with draft membraine, no trickle vents or air bricks.

No ventilation ever or was the ventilation blocked?

Suspended ground floor joists need airflow to keep them dry.

If it was never there, then it would have been a problem a long time ago, if it has been blocked recently, it may be a problem in development, unless I am misunderstanding you.




TLR - MHVR would not improve or reduce my attraction to buying such a property, as long as the price was not based on it being installed.

 

[dhutch]

No ventilation ever or was the ventilation blocked?

Sorry, no air bricks into the domestic living space, the under floor space remaining ventilated as designed.

TLR - MHVR would not improve or reduce my attraction to buying such a property, as long as the price was not based on it being installed.

Thanks.



Daniel

 

[dhutch]

Anyone else care to comment?

 

[maltaron]

If the property is airtight, how do you breath? or is it all recycled air? If so, then surely it is asking for disease.

 

[AronSearle]

If the property is airtight, how do you breath? or is it all recycled air? If so, then surely it is asking for disease.

With MHVR vents suck the air out, extract the heat, and blow in new air with the heat added, now you should see why air tightness is important as otherwise it simply doesn't work.

Airtightness is also just an expression.

about 10 air changes an hour is considered air tight for a new build, about 2< air changes an hour for eco/passive build (I might have these numbers wrong/approx).

A typical 1940-80s will easily have over 10 air changes an hour, so you waste a lot of money re-heating far more fresh air an hour than you will need.

You would need to do a lot of work to bring a 1940-80s house up to passive/eco house type airtightness levels.

 

[dhutch]

I guess it depends how you measure 'works'

At the moment I get lots of condesation on and around the windows and on the small sloping section of ceiling that is currently uninsulated.

I want to increase ventialtion to reduce condenstion, and one of the ways of doing this appear to be a MHRV system, as the costs are not that much greater than non HR systems, and leaving windows open onto the first notch is very wind speed sensotive and creates drafts on windier days.

As IM only in the house at evenings I cant leave the window open for an hour or two in a morning and then close it.

But as Im not planning to live in the house permantly the effect on reselling is relivent.

I apprciate im not going to get to the levels seen in an eco house, but as the question was asked i was trying to give an feeling for the current state of the house.



Daniel

 

[AronSearle]

Ok, well throw away any idea of it being better in regards to heating costs, you might break even, but it will probably add to your energy bill.

But it will eliminate the excess moisture and mould issue, a positive pressure fan will, but that can make the primary room quite cold.

As to your OP question, I am to biased, possibly joe public would be bought in that it's a good edition to the house, can't think joe public cares about the cost of heating a place when looking to buy.

 

[ladylola]

To answer your original qusetion , then no I don't think that I would purposely buy a house based on it having a system . From what I've read it seems to me all the cost of the heat you are saving goes in powering the system, and if the house isn't or wasn't designed with them in the first place then they will probably end up costing more as they won't be very efficient , which seems to be something of a self defeating end.
I've got an older house where it wouldn't be of much use so I am looking at adding heat through a passive solar system called a thermosyphon , a simple system that can be built from scavagned bits and pieces. Indeed I've just picked up some old double glazed doors to start building .

 

[dhutch]

To answer your original qusetion , then no I don't think that I would purposely buy a house based on it having a system.

Fair. But would it having one put you off the sale?

 

[ladylola]

No it wouldn't put me of buying the house, just because it's there doesn't mean I have to use it anymore than I have to use the aircon in a car if it's fitted.

 

[dhutch]

Sounds rational to me.

Obviously I dont envisage it slashing heating costs in half, because if nothing else at the moment we mainly just dont ventilate! But I can only see consistant and predictable low level ventilation being an asset to the comfort of the house, and I would be supprised if the energy used in circulating the air exceeded the energy recovered by the heat exchanger, although I understand on cheaper units its more marginal than prehaps it ort to be.

I guess I could do some sums based on preticted temperatures and air flows.


Daniel

 

[AronSearle]

Just did a bit of googling (briefly so I can't promise this is accurate)

I think the cheap basic models consume something like 20-60 watts, so it's going to cost you the equivalent of leaving a light on all the time, which is what, a couple of quid a month?

This makes the assumption your house is reasonably air tight, if not then the extra air leakage will make your central heating run a bit more, but again we are probably talking a few extra quid a month at best.