Old house: loft insulating

[Homeboy]

Hi.

I've recently moved into a top floor flat of a 100 year old tenement in Glasgow. A trip to the attic showed that there is no insulation, only lots of dust and old cables. The joists are spread approx. 15 to 15.5 inches apart to a depth of 6 inches. This seems too shallow for average roll-out loft insulation material and as the floor space in question is quite large I don't want to get involved in increasing the joist height. Are there any products that will give equivalent insulation effect to the recommended 270mm (though I have come across 200mm as the recommended depth in other sites - which is it?) but at only 150mm. I may also need to use the loft space for storage in future. I am a novice to DIY (first flat I've owned - no landlord to phone up with problems anymore!).

mnay thanks for any advice.
Eddie Brennan

 

[JohnD]

Well, start by insulating to the 6" of your existing joists. This first 6" will make a lot more difference than the second 6" (or 150mm if you prefer).

The reason being that the first 150mm cuts out (my made up figures here) 80% of the heat loss. So it cuts loss down from 10kw for your flat to 2kW, and so it will save you 8kW (which at 9p per kWh would save you 72pence per hour..

The second 150mm will also save 80% of heat loss.... but only from the heat that has escaped the first layer. So it will save 80% of the 2kW and will save you 1.6kW (which is 14.4 pence per hour)

Figures made up for simplicity.

If you own the loft, and will want to be able to walk about up there, it is very dangerous to put thick insulation all over the timbers, as you will not be able to see where the timbers are and will probably fall through the plaster.

So if I was in your position, I would roll down the first layer of 150mm insulation first, then think about counter-battening it before applying a second layer and/or boarding. it.

 

[Homeboy]

Hi. Thanks. That does make sense.

However something else needs to be cleared up: why vacuum the loft? Two website recommend this but a builder I spoke to said that it is unnecessary and would not give any real benefit. Not having to vacuum would be my preferred option as this would save on hiring an industrial vacuum cleaner & time (precious weekends), not to mention effort in dragging a vacuum around a loft

Thanks
Eddie

 

[JohnD]

I vacuum mine. I suppose because i like my house to be clean. An old loft gets very dusty and dirty, and I hope to be up there from time without needing overalls and a dustmask.

The builder won't have your pride of ownership, and is probably quite used to working in dirty and dusty conditions.

 

[Homeboy]

Thanks for all your help, John.

I take it that not vacuuming won't affect the insulation effectiveness. I too would prefer a tidy loft though my case is probably different to yours. The loft is under communal ownership (6 flat / apartments in the building) and while I can lay insulation, its not actually mine to use freely or exclusively. I have been advised by the building management company that it would be almost impossible to get the other owner occupiers to fork out for loft improvements (none of them use it at present), including cleaning, insulating or even just laying basic flooring. I am willing to pay & carry out the insulation myself, as being in the top flat I will be the main beneficiary.

Thanks
Eddie

 

[RigidRaider]

I'm just amazed to read that there's no insulation. As soon as you lay yours, you'll notice the difference. Then lay another layer going in the other direction. Don't worry about missing the joists - if you're the only resident going up there you won't do that, will you?

We had minimum insulation in our last house and we laid a second layer over the top. It reduced out gas bills by about 30% and made the house even warmer.

Since you live at the top of a pile of flats I expect you'll find it much warmer. Cooler in summer too.

Do shop around for prices as there's big variation.

 

[Static]

You may want to wait till the weather gets a little colder and the other flats turn their heating on. Ive known people who live in top floor flats to not need heating and have windows open all winter because the flats below them provide them with more than adequate heating ALL year.