House ventilation knowledge required

[Guest]

Discussion on the HIPS thread regarding the need for ventilation

I got a guy round to assess and quote for cavity wall insulation.  Basically they said that they could not do it unless I had ventilation bricks put in.  

Now I appreciate that the law has tightened up to avoid people being overcome by boiler fumes etc., but we have a modern boiler (two years old) with proper direct external venting etc. and two open fires + chimneys.  How much more ventilation should we need?  I am trying to keep the house warm, not turn it into a wind tunnel!

Any knowledgable input would be appreciated.

[JeffC]

Prob no help John but i had cavity wall insulation done about 8 years ago , I too had to fit extra vents in the lower outside wall to vent under the floor, I think its to do with dry rot or something or other, Mine had been blocked off but the guy told me that could lead to more problems later if I didnt open them up and add more     , I fitted the vents and cant say I found it any more draughty, we noticed the house to be much warmer pretty much straight away    

as an aside , we have lpg gas combi boiler (in the kitchen)  we have no window vents , I have an oak floor laid over the top of the original floor and I sealed the oak skirtboards when I fitted them to keep the house free of draughts etc ,  we also have an open fire that we burn coal/logs on in the winter, It has a flap on the back that you can shut off to stop the air escaping up the chimney , in our living room we have 3 radiators, when I have the back of the fire shut off for some reason I get a stuffy nose and my eyes stream when the heating is on  but Im fine when I open up the back of the fire again , so for me there is prob good reason for ventalation on modern houses as with out an open fire they wont have a flow of air, but why on earth my hot radiators should effect me in that way I havent been able to work out              

[Barry Ashcroft]

QUOTE

we also have an open fire that we burn coal/logs on

Same one you use for the dodgy logbooks and service history's Arfur?

[JeffC]

we also have an open fire that we burn coal/logs on

Same one you use for the dodgy logbooks and service history's Arfur?

rumbled    

[Vinny's Westie]

It will be a measurement of the room size and then the output of the fire, get yourself down to the library and find out from the building regulations what size vent you need.

I remember an old warm air heating unit we had mounted internally failed the yearly gas test because there was no ventilation and the flame throwback was quite large (melted wiring to unit).  The output in BTU's meant the room had to have a 80MM hole in the wall direct to the outside, that is some hole, to cure problem.

Had to do it to sell house as I could not get a gas certificate without out, wonder if the hole is still there?

[iiyama]

If you have a suspended floor fabricated of timber then you should have air bricks around the house anyway. They are usually in the course immediatly below the damp course.

If you have a suspended floor fabricated of concrete, (pot & beam), then you stil need to circulate air in the void below the floor but for different reasons.

If you have a solid concrete floor then you do not need air bricks as there is nothing to ventilate.

The air bricks should be sleeved through the cavity so as not to leave the cavity open.

Open fires should have ventilation according to building regs. This is generally a 9 x9 airbrick which is again sleeved through the cavity. If you have a suspended floor you can utilise the air flow beneath the floor and vent the fire locally. This stops drafts flowing across the room.

If you need anymore info then drop me a line!

[Lurksalot]

 Basically they said that they could not do it unless I had ventilation bricks put in.  

If you have suspended floors on the ground level I suspect that it is as jeff says ,vents below the damp course to keep the air circulating under the floor .

We glazed a house for a friend a few years ago and he couldn't light his open fire unless he opened the windows because the house was so airtight he couldn't get the flu to draught

[Terry Everall]

The issue is not only about air for boilers etc but in old houses with single glazing and uninsulated walls moisture could escape and air canges were good

Mosern houses are centrally haeted and also cavity wall insulated so there is a reduced "flow" of air but also condensation builds up due to wet damp air not being able to escape. So it condenses on cold wall with poor air circulation and you dont want that so you need more air bricks