Earth Notes: KEHS talk: Draughts, Insulation, Ventilation (2024)

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So we all want to have warm homes and consume less energy.

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I think one of the things perhaps to understand when you're talking about houses,

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and I'm talking mostly about houses, not flats, is that they come, I mean,

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they're two basic sorts, particularly in Kingston.

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They're the houses that were built before the Second World War,

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which are one sort of house, so, and there's,

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they're houses built after the Second World War, and particularly more recent houses.

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So you might have heard the phrases "solid wall construction" and "cavity wall construction".

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So the houses that were built before the Second World War are mostly solid walls.

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We often call them brick-thick walls, sometimes rendered.

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They have raised timber ground floors, so they're lifted off the floor,

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and there are air bricks, which ventilate those timbers under the floor.

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They used to have single-glazed windows when they were built,

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and they have a loft space with a pitch roof.

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The other sort of house, which I'm talking about,

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which are more recent houses, might have a cavity wall more commonly,

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might have solid floors, although they could still have suspended floors,

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and might have been built with double glazing,

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and they might have some sort of loft insulation.

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So there's already a performance gap between those two sorts of houses,

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and houses that are being built today are just such a distance away

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from those pre-Second World War houses in terms of energy consumption;

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it's unbelievable.

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So one of the issues, really, that faces us in somewhere like this,

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where probably 75% of our stock in Kingston might be before the Second World War,

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I'm guessing a bit, but it's quite a lot, anyway, of all we have.

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So how are we going to make those houses perform better?

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Because it does help if the house performs better,

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if it doesn't lose as much energy when energy is becoming more expensive,

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and we want to produce it sustainably.

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So one of the things everybody looks at, draughts and air movement,

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because those are big factors in heat loss.

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I think it's, Damon would probably correct me, but I mean,

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it's something like 25% of our heat losses.

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30% is through ventilation ...

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... unplanned ventilation.

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So even if you've insulated the walls,

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if you've got lots of gaps everywhere,

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you're still going to be using a lot of heat.

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Of course, as you start to shut up these gaps,

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you are keeping moisture within your house,

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and that's the root of a lot of the problems we're beginning to see.

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You know, we've heard of, I think it's called Abassa's Law,

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a little kid who died of a mould in his home,

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because when you start to put in double-glazed windows,

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you're starting to reduce that airflow.

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So the whole issue of draughts / ventilations is very interlinked here.

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So in older houses, this diagram just shows,

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in older houses we used to have the air, wind brought in air.

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There were gaps in the house.

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You had chimneys pulling the air out through the house.

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That provided a natural circulation of air

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and kept moisture levels reasonably low

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and kept us cool in summer.

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So as we start to...

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As we start to put double-glazed windows in,

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this is the kind of thing you see,

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where that's a double-glazed window.

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If you then shut up your fireplace,

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which is something you want to do,

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I mean, you want to close up your fireplace,

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but you've got to pay attention to bringing some fresh air in,

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and not letting too much moisture accumulate

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to avoid this kind of dampness.

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And if you look at pictures of places

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which are identified as being damp,

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this is often what you see.

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And it's not dampness in the way we used to think of it

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when it was water coming up through the walls

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or rain being driven through the walls.

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It's dampness internally.

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Because we take showers, we cook,

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people sometimes dry washing indoors,

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particularly in flats, it's quite a common problem.

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And we breathe, and that all creates this sort of difficulty.

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So you have to be careful what you're doing.

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So this is about ...

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This is about where you might want to seal your house up

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to try and lose these, to try to stop the loss of heat.

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And a very common problem that people are not really very clear about

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is when you...

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There was a trend for having timber floors,

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exposed timber floors in the '70s, I guess.

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Lots of people sanded their floors.

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I mean, I just mentioned earlier on that the...

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There are air bricks on the outside of the house

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and there's a continuous passage of air under it.

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Well, that is leading to quite a lot of heat loss,

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and people sometimes don't appreciate that.

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So when you put fitted carpets in,

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of course you're sealing off that area

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and you are reducing the heat loss through that.

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But all these places lose heat and energy.

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So... But you can start to do some things.

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I would really recommend anybody who's living in a house like this

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that's got timber ground floors.

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I'm just talking about ground floors here.

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First floors are irrelevant because they're already inside the shell.

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But ground floors, if you're having your carpet refitted,

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it's really worth taking the opportunity to...

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I mean, this is disruptive, but it's worth it.

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Take all your furniture out of the room.

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You've got to take it all out to have it refitted with a carpet anyway.

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Lift the floorboards up and put insulation between the floorboards.

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And that's... The way these things are done is you can see

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that the timber joists are still exposed,

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so it's still got air circulation under it,

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which stops it rotting because often the underfloor spaces

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are a little bit damp.

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Put it and then put insulation in between,

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and that will help to reduce your heat loss

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before you put your carpet back on.

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I mean, modern houses all have pre-insulated ground floors.

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Yeah. I suppose you might not recognize it,

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but when you take the floorboards up on your floor,

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that's what you see. You see this pattern of floor joists.

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The thing is that the cavity walls,

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your house either has a cavity wall or it doesn't.

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And there are probably relatively few houses in Kingston

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that have cavity walls.

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So that is not an option for a lot of people in Kingston to do this.

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So there are a couple of options if you haven't got a cavity wall.

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One is internal wall insulation and one is external wall insulation.

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So just starting with internal wall insulation,

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that's where you're adding some kind of insulating material

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on the inside of the walls.

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And there are some... I mean, there are some problems with this.

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I mean, it's quite expensive to do.

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It's quite disruptive.

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And you have to be careful about where...

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You can create a situation where you get condensation inside that wall.

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So condensation occurs.

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So you've got the warm side of the room where he is.

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Then the temperature is dropping through the wall

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to the temperature it is outside.

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And if you allow moist air to pass through that construction,

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it will condense somewhere in the middle of that.

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So you've got to... If you're not careful.

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If you're not careful, yes. So it's got to be done quite carefully.

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And the other problem with this, obviously,

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is you've got mouldings in a Victorian house.

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You have to replace those.

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But you can do it and it can be made to work.

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There are some other problems with cold... with joists and things.

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Anyway, so it's tricky.

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And this is why, in a way, people are not doing this so much.

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It's better to do what you can do reasonably easily in a way

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and then have an air source heat pump,

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which, if we're all worried about the climate,

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is what's really going to make the difference.

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So that's the external option.

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Now, I mean, there are quite a lot of rendered houses in Kingston,

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and that is an option for them.

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And it is quite a good system because it does...

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It makes the whole...

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It is putting a tea cozy round the house, really,

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and it will reduce it.

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But that is quite an expensive thing to do.

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But it's not hundreds of thousands to do that.

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I mean, I think that's more like 25...

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This is the thing that most people do,

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and it is the thing that you should all do.

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And if somebody says to you, they've insulated their loft,

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if you look at the depth that they're talking about here,

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because the depth has risen and risen and risen

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since I've been working on buildings.

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So it used to be 100 millimetres

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and we're now at nearly 300 millimetres.

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So it is well worth everybody making sure that your loft is properly insulated,

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because that's an easy thing to do.

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I mean, I say it's easy, because it isn't that easy,

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because we all fill our lofts full of a load of rubbish.

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And then you've got to...

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If you want to put that rubbish back,

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you've actually got to build a platform on top of it

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to let the insulation run under the top.

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But it is still, relatively speaking, the easiest thing to do.

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So well worth considering.

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Now, the other thing to understand is that the physics of houses

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is relatively simple, but you ventilate.

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That space under your roof, you really want to ventilate,

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because moist air will rise up through your ceilings.

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And I talked about moisture condensing.

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What you do with the roof, where it rises through the loft,

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you have to keep it ventilated so that that moisture will be dispelled.

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If you close up all your eaves and seal everything off,

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and that can be a problem with some sorts of insulation system,

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the thing won't perform properly.

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But I mean, most traditional houses have eaves ventilation.

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If you go up in your roof space,

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you can often feel a bit of air movement, and that's a good thing.

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That's what you want, provided your insulation is at ceiling level.

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That's just repeating that.

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And that's talking...

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This is a trickier problem to insulate

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where you're following a line in the ceiling,

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and you haven't got a big depth.

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And there are various solutions to that.

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You can actually put the insulation on the outside of the roof,

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or you have to keep a ventilated void on the other side of that,

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again, to dispel the moisture.

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Or you can go for trying to completely seal it from the inside.

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But it has to be carefully thought through.

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And that's a bit more of a discussion.

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This is how you prevent the condensation of the roof space

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by bringing the air in at the eaves.

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Now, the other thing to talk about is...

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So when you've done all this, if you do a lot of sealing up,

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then the question is,

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how do you make sure that you don't get this condensation

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I've been talking about?

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So the building regulations has some solutions to that.

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So when you...

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They ask you to put...

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There are various ways of doing it.

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One way of doing it is to put what we call "trickle vents" in your windows.

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So if you look at...

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when people have replaced their windows,

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you'll often see these little grilles at the top with a sort of flick,

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so you can have them open or shut.

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And that's what that's about.

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That's supposed to be providing a little bit of fresh air into the home.

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And then they're also building regulations

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for having fans in your bathroom and your kitchen.

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Again, that's another place.

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That's where you're generating the moisture,

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because you want to get that out of the room.

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A more sophisticated approach

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and what happens in new buildings now is something called...

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is a system where you actually extract the air

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and you pass it through a heat exchanger somewhere in the building,

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maybe in the loft or in a hallway.

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And that preheats air coming in,

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so that's an even more efficient way to do it.

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But what's particularly dangerous is if you don't do any of those,

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if you put in double glazing,

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you seal up your chimneys

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and you seal up all the ... draught proof the doors,

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and then you don't do anything else about ventilation,

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you are in danger of getting condensation in the building.