House ventilation/air recycling systems (HRV)

Hi,

My Mum lives in a 1960's bungalow with reasonably good insulation , cavity walls and double glazing. She gets a lot of problems with mildew behind cupboards and condensation on aluminium window frames. Two internal walls are single skin but shared with the integral garage, so these walls get colder.

My feeling is that the house does not have adequate ventialtion so was wondering about systems which pump out stale air and pump in fresh air, transferring heat from the former to the latter .

The bungalow has a huge accessible attic space and her kitchen and bathroom both have false ceilings, si I assume any vents could be placed easily out of site.

I took a look at the xpelair site but the range of systems is bewildering. I wonder if :

a) Anyone thinks this is the right approach

b) any experience of the cost and which products are suitable

c) I also have read of systems which create a high air pressure indoors . forcing air out. Is that a better approach ? I assume heat is forced out too !?

Reply to
jonathan.ives
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Insulating these walls would be fairly simple, as it could be done on the garage side.

It is usual to not include kitchen extraction on these systems, as kitchen air is often greasy. Bathroom/shower extraction and tumble dryer heat recovery are usually good bets.

However, it's possible that simply using kitchen and bathroom extractor fans to remove moist air at the point of creation would help, also opening bedroom windows in the morning to air the room, before going down the heat recovery route.

Owain

Reply to
Owain

At the moment these are expensive units, usually only sold through specialist installers. You're looking at =A31500+ for a typical system from the research I did. The cheapest whole-house unit I could find is made by Kair. They sell the parts online, so you avoid the sales/design/install costs. Their unit is about =A3600 + ducting/vents/etc.

It will be cheaper to extract at source, so putting an extractor in the bathroom and the kitchen. While these do waste heat, you have to consider the total cost over the life of the system. They would also use very little electricity. Or you could fit a couple of single room heat-recovery units (e.g. BES sell a unit for about =A3180). I've noticed thes pop up on eBay from time to time.

I think as the building regs get tighter, it will soon be effectively mandatory to have some form of MHRV in new builds. The greater volume should then push prices down to more realistic levels.

These require a very airtight building - you don't want the damp air to be pushed into the loft.

Having been put off by the costs of these units, I'm having a go at converting a large (microwave oven size) commercial single-room Toshiba MHRV unit I picked up for practically nothing on eBay recently. I plan to mount this in the loft in an insulated box connected to ducting, extracting air from the bathroom and kitchen, and blowing fresh air into the main bedroom and lounge. A bit Heath-Robinson, I know, but the whole lot should come to less than =A3100, and it's an interesting little DIY project.

-Antony.

Reply to
Antony

Yes

A single fan costs about £150 a system from £900- £2500plus. I was looking into it recently (Google) but decided it was too pricey.

My sister is onto her second system of that type. It made the hall cold, but she's now on staywarm tarrif so it doesn't matter to her to increase the heat. I suspect the current one (with fancy controls on fan speed) is cheaper to run (including heating fuel) than my dehumidifier is.

A dehumidifier is another option.

Reply to
<me9

Try a hygrometer first, to get an idea if the problem really is high humidity and not just condensation on cold surfaces.

If humidity is high, say above 60% then try a dehumidifier.

In any case try insulating behind cupboards on outside/cold walls with a sheet of thick-ish polystyrene.

Condensation can be endemic on aluminium windows if they're older and don't have a 'thermal break'

cheers, Pete.

Reply to
Pete C

Open some windows?

Mark

Reply to
Mark

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