199 lines
6.8 KiB
Plaintext
Executable File
199 lines
6.8 KiB
Plaintext
Executable File
property
|
|
propertyadvice
|
|
jeffhowell
|
|
5387409
|
|
-----
|
|
# Loft insulation: stave off winter bills
|
|
|
|
## Now is the time to insulate your loft. Jeff Howell advises on how much you
|
|
need and what it will cost.
|
|
|
|
![Loft insulations: cut winter fuel bills][1]
|
|
|
|
By Jeff Howell 7:00AM BST 27 May 2009
|
|
|
|
[Comments][2]
|
|
|
|
If you are still getting over the shock of last winter's heating bill, then
|
|
you're probably not alone. Fuel prices are at a record high, and Britain's
|
|
recent winter temperatures have been the coldest for 13 years. Where's that
|
|
global warming when you need it?
|
|
|
|
Some scientists, who question the reasoning behind the carbon dioxide-induced
|
|
climate-change theory, are suggesting that we might actually be entering a
|
|
period of global cooling, rather than warming. But whether your motive is
|
|
saving the planet, or simply keeping warm, it is clear that thermal insulation
|
|
is important. The question is, how much insulation is realistic, and which
|
|
materials are the best?
|
|
|
|
Current government advice for loft insulation - as specified in the building
|
|
regulations for new homes (which, it must be stressed, do not apply to
|
|
existingproperties) is to have 270mm (10½in) thickness of insulation above the
|
|
top-floor ceilings. I am indebted to Sunday Telegraph reader Peter Williams,
|
|
who has asked me to explain exactly what this means.
|
|
|
|
It's a very good question. Different insulation materials have different
|
|
properties, and 270mm of one material might perform better or worse than
|
|
another.
|
|
|
|
Unfortunately, our present Government displays about as much understanding of
|
|
energy conservation as it does of banking, and it seems to think that if it
|
|
tells us to put 270mm of "insulation" in our lofts, then we will obey, and all
|
|
live happily ever after.
|
|
|
|
So let's get down to basics. The 270mm figure is based on fibreglass, chiefly
|
|
because this is at present the cheapest insulation material. If you started
|
|
with an uninsulated loft, and added this depth of fibreglass insulation, the
|
|
trade price for materials would be about £5.30 per square metre.
|
|
|
|
The 270mm figure comes from calculating the depth of fibreglass required to
|
|
provide the current loft insulation standard of 0.16W/m2K (watts per square
|
|
metre per degree Kelvin) - referred to as the U-value. U-values are like golf
|
|
scores - the lower the better.
|
|
|
|
Now, as many readers have found out, the problem with putting 270mm of
|
|
insulation between the top-floor ceiling joists, is that most joists are only
|
|
100mm (4in) deep, so the insulation stands well proud of the joists,
|
|
preventing them being boarded-over for storage. There is no point compressing
|
|
the insulation to squash it in, because this removes the air spaces that
|
|
provide the insulating effect.
|
|
|
|
If you want thick loft insulation and a boarded loft space, the only realistic
|
|
solution is to deepen the joists, by adding extra timber on top of them (or,
|
|
better still, to insulate between the rafters instead, but that is a separate
|
|
topic). The depth required can be reduced by using a more efficient insulating
|
|
material. However, most fibrous insulation products have similar properties to
|
|
fibreglass.
|
|
|
|
Mineral wool fibre loft insulation (sold as Rockwool), would also need to be
|
|
270mm deep to achieve a U-value of 0.16. Mineral wool fibre is claimed to be
|
|
less irritating to the installer's skin than fibreglass, although my own
|
|
experience is actually the opposite. It is also more expensive than
|
|
fibreglass, and would cost around £8.20 per sq m.
|
|
|
|
Fibreglass is also available "encapsulated" in a metallised polythene film
|
|
(such as Knauf's Space Blanket), that makes it completely non-irritant to
|
|
install. Two layers, totalling 300mm (12in) would cost about £12 per sq m.
|
|
|
|
The most thermally efficient insulation material is polyisocyanurate, or PIR,
|
|
sold as lightweight rigid foam boards - Kingspan, Celotex, and some other
|
|
brand names. The 0.16 U-value could be achieved using a PIR board 175mm (6¾in)
|
|
thick.
|
|
|
|
The disadvantages of PIR board insulation are its cost - about £21 per sq m to
|
|
achieve the 0.16 figure - and that, being rigid, it has to be cut accurately
|
|
to fit it between joists or rafters. This is easy enough in a relatively
|
|
modern house, where the joists are likely to be evenly spaced, but in an older
|
|
property it can be time consuming to measure and cut each piece to fit.
|
|
|
|
Many readers have asked about multi-foil or multi-layer insulation. This is a
|
|
30mm (1¼in) thick quilt, comprising 14 or more alternating layers of metallic
|
|
foil and thin foam, which the manufacturers claim has an insulation value
|
|
equivalent to 200mm (7¾in) of fibreglass. However, this has been queried by
|
|
scientists at the Building Research Association and the National Physical
|
|
Laboratory, who say its actual insulation value is only about one-third of
|
|
that.
|
|
|
|
But what about the latest green insulation products? Sheep wool is used to
|
|
make rolls of loft insulation, similar to those made from mineral wool fibre.
|
|
It is about 20 per cent more efficient, meaning the benchmark 0.16 U-value can
|
|
be achieved with a depth of 225mm (8¾in). It is a non-irritant material, and
|
|
the manufacturers claim that wool's natural ability to absorb moisture in
|
|
humid conditions, and give it off when dry, can help maintain stable
|
|
temperatures within a building.
|
|
|
|
Its one disadvantage is cost - from about £20 per square metre to achieve the
|
|
0.16 U-value. The manufacturers do claim it will retain its shape and thermal
|
|
properties for the lifetime of the building, however, unlike fibreglass and
|
|
mineral wool fibre, which will eventually degrade and collapse.
|
|
|
|
[X][3] Share & bookmark
|
|
|
|
Delicious Facebook Google Messenger Reddit Twitter
|
|
|
|
Digg Fark LinkedIn Google Buzz StumbleUpon Y! Buzz
|
|
|
|
[What are these?][4]
|
|
|
|
* Share: [Share][3] [ ][5] [ ][6]
|
|
|
|
[Tweet][7]
|
|
|
|
http://www.telegraph.co.uk/property/propertyadvice/jeffhowell/5387409/Loft-
|
|
insulation-stave-off-winter-bills.html
|
|
|
|
Telegraph
|
|
|
|
## [Jeff Howell][8]
|
|
|
|
* ### [Lifestyle »][9]
|
|
|
|
* ### [Property »][10]
|
|
|
|
* ### [Property Advice »][11]
|
|
|
|
* ### [Green Property »][12]
|
|
|
|
In property
|
|
|
|
[![Silver birch is unlikely to cause damage to a nearby building][13] ][14]
|
|
|
|
### [Home improvements: Could my neighbour's trees damage my house?][14]
|
|
|
|
[![DIY skills learned from dad, such as carpentry, are in sharp decline partly
|
|
because of advances in technology
|
|
|
|
][15] ][16]
|
|
|
|
### [DIY: Are dad skills obsolete?][16]
|
|
|
|
[![Jeff Howell][17] ][18]
|
|
|
|
### [Home improvements: Do I need to replace my locks?][18]
|
|
|
|
[X][3] Share & bookmark
|
|
|
|
Delicious Facebook Google Messenger Reddit Twitter
|
|
|
|
Digg Fark LinkedIn Google Buzz StumbleUpon Y! Buzz
|
|
|
|
[What are these?][4]
|
|
|
|
Share:
|
|
|
|
* [ ][3]
|
|
|
|
* [ ][5]
|
|
|
|
* [ ][6]
|
|
|
|
* [Tweet][7]
|
|
|
|
* Advertisement
|
|
|
|
![][19]
|
|
|
|
telegraphuk
|
|
|
|
Please enable JavaScript to view the [comments powered by Disqus.][20] [blog
|
|
comments powered by Disqus][21]
|
|
|
|
Advertisement
|
|
|
|
sponsored features
|
|
|
|
Loading
|
|
|
|
Classified Advertising
|
|
|
|
* [UK Homes][22]
|
|
|
|
* [Overseas][23]
|
|
|
|
* [RHS Chelsea][24]
|
|
|
|
Loading
|
|
|
|
var puffs_8314099 = new Array();
|
|
|