Loft insulation: board it over?

What is that supposed to mean ?

Reply to
Mike
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Please pay attention, that was a general statement. Duh

That is right, but you can't do it right.

usable space in a roof? You pack in as much as you can

Nor so, as the target is constantly moving.

How odd. This sounds like two wrongs make a right.

Did you know that?

Reply to
Doctor Evil

You are making things up again.

Reply to
Doctor Evil

Aggggggghhhhhhhhhhhhh .... lalalalalalalalaalalalala ...

For God's sake change the record!!! How many years has this argument been going on!? You will never understand the meaning of the word "impractical" so just give up while you're behind and agree to differ for once!!!

a
Reply to
al

Yet another example of legislating about irrelevances.

Reply to
Andy Hall

Then you should make that clear.

Uh huh.....

Space in houses is at a premium as you always point out when advocating installation of combi boilers even in totally inappropriate applications.

Filling up loft space with unnecessary insulation and wasting usable storage space is nonsense.

The energy costs might be, but the difference in heat loss does not. you are arguing about a second or third order effect and not paying attention to the first order effect of the loss/gain through other surfaces.

You didn't ever study physics or engineering did you?

Reply to
Andy Hall

No, you place the insulation where it will save the most energy, you don't blindly follow rule of thumb advice.

If that means with 200mm in the loft you reduce the total contribution made by the loft to the whole house heat loss to 5% of the total, upping it to 400mm will be of no practical value. Try to do something about the

95% not the 5%

Your statement defies logic.

Reply to
John Rumm

That will depend on the circumstances...

If all you had before was 9mm of plasterboard, then addition of 3/4" of chip would result in a *very* significant reduction in losses (especially as it could potentially trap an additional 4" of air between the PB and chip).

Not at all, it will help reduce the chance of dry rot taking hold. If you seal off all the air flow to the existing timbers then you compound the damage that can be done by any moisture that makes its way into them.

Again not worth doing, you add extra load to the loft joists, and create a thermal bridge.

If you want more insulation than you can fit between the joists, and you also need a floor down over it, then you would be better off skipping the insulation betweent the joists altogether, and using a rigid foam insulation board right over the joists and sitting the floor onto those.

This would be in effect creating a warm deck roof type structure that keeps the joists inside the thermal envelope of the house.

You must learn to think more.

Reply to
John Rumm

Once again: "The insulation value 3/4 of chipborad is neglibible."

The loft is vented and this will not occur.

The loft is vented and this will not occur.

Wrong! Is worth going as you get 8" instread of 4" of insulation.

As does the chipboard and stored good on top, which all must be taken into account.

Only the points where the joists meet, which is more than offset by the inscreased insulation thickness.

Rockwool is cheap and best filling in void spaces.

More expense and will eliminate any cold bridge. The only siensible thing you have said.

1/10 You are very good at this. Very poor Need to try harder.
Reply to
Doctor Evil

I know. He is incapable of learning of basic common sense. Sad but true.

Reply to
Doctor Evil

What evidence do you have, beside making-up-ness, to support this? Nah, don't bother. It is clear you are not very good at this.

Reply to
Doctor Evil

That is correct.

The edges of the loft cannot be used for storage. The loft is a large void and installing proepr levels of insulation is very easy, the easiest part of the house to install insulation.

That is the target.

I am brilliant at physics.

Reply to
Doctor Evil

In the situation I described (no insulation at all, 9mm PB), the addition of 3/4" of chipboard would reduce the losses through the loft by over 50%. How can that be "neglibible" (sic)?

The loft may be, however you are proposing burring the joists under 8 inches of rockwool.

If you use rigid panels as I described you can have as many inches of insulation as you want - you still don't need the wood.

Correct, so lose the wood and reduce it.

Air is good as well and much cheaper.

You are the one who was advocating cramming in as much insulation as possible irrespective of cost of benefit.

How quaint, its like the infant marking his teacher.

Reply to
John Rumm

Typical 2 storey detached house 9m x 6m on plan, walls 0.35, ground floor 0.22

200nmm roof insulation: U-value 0.182 Total bldg heat loss 102.9W/K 400nmm roof insulation: U-value 0.095 Total bldg heat loss 98.2W/K

Net reduction 4.56%. In cash terms probably £4-5p.a. saving

Cost 200mm quilt 54m2 @ £3.75m2 = £202 (+labour). And if the house has a 30 degree roof pitch you've reduced the usable loft space by

6.2m2.
Reply to
Tony Bryer

Once again: "The insulation value 3/4 of chipboard is negligible."

"Water vapour" rises through the insulation and chipboard and into the loft.

You can install rigid foam of course and for the thickness it performs brilliantly. But not worth it in a loft when the same insulation performance be achieved cheaper.

Depends on what the loft can take. If it can, as most can, then use 4x2s

You don't know much about this stuff do you?

Reply to
Doctor Evil

And when fuel prices rise, which it will, that £5 will be £15 and increases as the years roll on. So the pay back is a lot quicker than you think. Then there the point that fuel prices rise, so do building material prices. So in a few years when fuel has risen and you want to put in extra insulation the Rockwool price has risen too. Then there is the point that insulation regs are being hyped up soon and you will be ahead of the game making your house more saleable. Then there is the point of keeping the heat out and

400mm does that much better than 200mm.

All in all, well worth doing.

I've seen Rockwool cheaper than that.

Reply to
Doctor Evil

This is a specious argument. An alternative change to the building that costs the same but saves 200 pounds a year rather than 5, would then be saving 600 a year. Making the loft insualtion look even less attractive.

The more fuel prices rise the more important it becomes that you target your energy loss reduction efforts on the major causes of energy loss rather than titing with the minor ones.

But by your own argument the payback has increased in direct proportion making this irrelevant.

Clutching at straws now I think. Most folks are going to be happy it "has a fair bit of insulation", I can't see them caring whether it is

200 or 400mm. It is just not that important. They will probably be more interested that the local school has a good reputation, or there is off street parking.

But not as well as a roll of solar film for the big south facing patio door though.

Or not...

Again look at the whole picture first - then decide if it is worth doing. Chances are there will be plenty of more worthwhile jobs that need doing first.

The money you would spend on having insulation added to the loft could also be spent on a upgrade to a programmable room stat and adding a TRV to each radiator. This would save far more energy and have a much faster payback.

For the money you could fit alot of draft excluders, or add secondary double glasing to the largest and most lossy windows. Again far more result for your money.

So what? compared to the cost of having it installed (especially if you are going to tit about with extending the ceiling joists), makes the price of the material "neglibible" as you would say.

Reply to
John Rumm

Aggggggghhhhhhhhhhhhh .... lalalalalalalalaalalalala ...

On the plus side, 400mm of insulation is plenty to hide a corpse.

Reply to
Ian Stirling

They most certainly can. It depends on what you want to store and how you go about fitting out the space.

Reply to
Andy Hall

I suspect that he never learned the word "context" at school.

Reply to
Andy Hall

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