Whole House Fan

[Rick Hughes]

Anybody know if these can be purchased in UK .... would seem a great solution.

[Bob Minchin]

If it is what I think it is, then yes there are lots of suppliers Google for domestic heat recovery systems.

Bob

[dennis]

Its a terrible solution to a problem that doesn't exist. It sucks and it needs to blow.

If you want mechanical ventilation then look for a whole house heat recovery system.

Then you can have clean filtered air replacing the old stuff and you can have positive pressure so it keeps all the dust, pollen, etc out.

They are not easy to fit as they need ducts to the various rooms to work properly, but they should make a good DIY job.

[harryagain]

There are lots of them. In the UK they are called "whole house ventilation systems". Usually they have heat recovery ie the outgoing air warms the incoming with a plate heat exchanger.

I have seen lots fitted. After a while the owner realises they are a complete waste of money, time and energy. They also consume electricity and require periodic new filters and maintenance.

So they shut them down and go back to opening a window.

A few years back they were considered to be the dogs bollocks but now almost defunct.

[Tim Watts]

On Tuesday 09 July 2013 17:40 harryagain wrote in uk.d-i-y:

They look like a good idea, and superficially simple. Until you realise you have to either have lots or a load of 4inch duct running back to a central; point (this is often non trivial to arrange).

As you say, I suspect the griming up of the plates and the filters is where they fall flat.

My bathroom extractor vent needs hoovering quite a lot as the grill attracts clothes lint and fluff. The outlet grill has a mesh that needs a clean off once a year. After 3 years of intense use (landlocked bathroom, needs the fan running a lot) the fan blades sound like they need a good clean as they are making a lot of chudder-chudder type noise.

That's one fan in a very simple setup.

Dread to think what a whole house usint would look like by now on the inside.

[Davey]

We rented a house in Kansas City with one of these Whole House Fans. It blew into the roof space, which itself had those shiny rotating heat-vents that send pigeons dizzy when they sit on them. The fan worked a treat. If we came home after a weekend away, and the house was hot, ten minutes of the fan running brought it back to a sensible temperature. It drew the cold air up from the basement, and blew out lots of hot stale air. It sounded like a jet engine, though, so was used only when necessary.

[Rick Hughes]

I did try 3 of the main names in MHRV systems, none of them supply these.

[Rick Hughes]

I have a full whole house Mechanical Ventilation System ... provides heat recovery and filtered air, including electrostatic filters as well. So I am fully up to speed on these .. had one in past 3 houses.

The issue is the house is getting too hot - currently :-)

Having to put a fan in each bedroom ... noise & running costs.

I like what I saw on the US program... I don't follow that is is a terrible solution ..... heat rises so all hot air in house ends up, upstairs ... this system vents that hot air into the attic. To be replaced by cooler air from vent downstairs ... what is so terrible about that ?

In fact the BBC had a n item that if you are overheating in a house open loft hatch, and use a fan to blow air into loft ..... inefficient version of same thing.

[Rick Hughes]

I have one - disagree, would never have a house without one, on my 3rd build with one. Maintenance is washing filters once a year.

Meets Bld Regs ... without need for window trickle vents.

However this is not the Whole House fan as per the video ... separate thing completely.

[Rick Hughes]

On a self build easy to design system so all ducting ... 150mm main and

100mm branch was hidden ..

There are incoming & outgoing filters so heat exchanger keeps clean ... I have 3 stage filtration on incoming incl electrostatic filter (stops pollen)

I open unit once a year remove all filters, wash then hoover out any dust and that is all it needs.

[Rick Hughes]

That is exactly wny I am thinking of getting one .. only use when you need to , quickly vents house and cools it down .... they are variable speed DC fans, so should avoid noise issue once bulk is vented.

[Davey]

The one we had had no heat exchanger, no filters, just a big fan with automatic shutters underneath it. Mains powered.

[dennis]

Convection will probably be enough without the fan if you just want to get rid of hot air.

Funny enough I have my hatch open ATM to try and cool stuff down. I was thinking about fitting an extractor in the loft door but then I would need better ventilation in the attic.

What I really need is some solar panels to reflect the heat away. 8-)

[Davey]

Presumably you haven't lived in Kansas City in summer?

[harryagain]

That actually happens. With an IR camera in the loft, my PV panels were clearly visible as a cooler "shadow" on the underside of the roof.

[js.b1]

It is a big panel fan, speed control, and shutters.

You could DIY a similar solution with the loft door - fit a panel fan or in dustrial extractor fan of at least 12" diameter.

From own experiments (South Facing)...

- Two 6" extractors (120L/sec, 37dB(A) each) upstairs in a top window fan p anel & a window open downstairs keeps THAT room near outdoor temps once the sun has gone off it. It really needs three such extractors (180L/sec or 64

8m3/hr). Sun blinds (as with air conditioning) are really important re sola r gain. Outdoor blinds or screens work better than a roller blind inside.

- Whole house would need double to triple that, aim for 1600m3/hr minimum a nd really go for 2000-3000m3/hr if you can.

You may want to create simple timber frames with stretched-over flyscreen o n the "intake" windows to avoid the inevitable parade of insects, swearing, banging :-)

Ebay has various industrial fans, some a bit suspect in terms of spec/quali ty/design. A DIY shutter lined with 50mm Celotex will make its contributory heat loss inconsequential as long as it is airtight (neoprene round bulb s eal, marine or higher quality draught proofing).

[js.b1]

Correction - that DOWNSTAIRS room close to outside temps.

You really need A LOT of m3/hr to shift the heat out, solar gain is the rea l enemy here even if you super-insulate the walls. Everything you can do to minimise solar gain will improve matters considerably - vertical sun brake s work well and avoid any view obstruction (stick out horizontally from a w all above a window with louvres set at the correct angle to eliminate peak sun ingress into the room).

[Rick Hughes]

On 10/07/2013 14:02, Davey wrote: one we had had no heat exchanger, no filters, just a big fan with

Yep that is the type I was thinking about - only used during heat spells'

[Rick Hughes]

Only thinking of using it at night once sun has gone down to vent the build up of heat on 1st floor. House is highly insulated ... but once it's in heat stays :-(

[Grimly Curmudgeon]

My loft hatch has been open the past ten days and nights and made no appreciable difference to the room temperature until last night, when the back room was at 26 and the front room at 28 (both were sitting at

28 and 30 all week). This surprised me, as the attic has a massive passive roof vent right on the ridge, which was originally designed as a whole-building vent, along with two others along the way. Before I ceilinged the back room the roof vent did work, but I suspect the flow of air was such that it went up the sloping original inner ceiling, thus to the vent. There was a noticeable pleasant coolness to that room in summer pre-ceiling.