Loft Insulation

Page 9 of 10  


I prefer to stick to using information with demonstrable and known figures.
What-if scenarios are a separate topic.

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

Then you agree with me then.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 14/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No.
.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

You have just contradicted yourself.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.564 / Virus Database: 356 - Release Date: 19/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Dean Richard Benson wrote:

why not use this http://stardust.jpl.nasa.gov/tech/aerogel.html stuff? OK it's a bit expensive ($11/gram) but hey, when you want the best. . . . 'It's the lowest density of any solid, and it has the highest thermoinsulation properties. Though it would be very expensive, you could take a two- or three-bedroom house, insulate it with aerogel, and you could heat the house with a candle. But eventually the house would become too hot.'"
Nick
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Wed, 21 Jan 2004 16:16:10 +0000, Dean Richard Benson

You can do the sums on this.
Calculate the heat loss for the area of the ceilings.
For a pitched roof plus 100mm of insulation, the U value is 0.35
So, let's say the house is 7m square for the sake of argument.
Using conventional central heating temperature assumptions of -3 degrees worst case outside and 18 degrees in the upstairs rooms, the heat loss will be
Area x U x temperature difference
or 7 x 7 x 21 x 0.35 = 360 Watts
If you have 150mm of insulation, the U value falls to 0.25 and the heat loss will be 257W.
With no insulation, the U value of the pitched roof is about 2.0 and the heat loss about 2kW.
You can see that there is a huge difference between nothing and 100mm, but a rapidly diminishing return after that.
This is typical worst case.
However, averaged over the year, the outside temperature is probably closer to 10 degrees, so assuming continuous heating at 100mm of insulation the loss is 223Watts and at 150mm about 160W. With 200mm you would get down towards 120W.
100W of heating by gas at a price of 1.4p per kWh works out to just over 12 per annum.
In terms of the material cost, this provides a reasonable rate of return. However, if you set it in the context of whether the space is important to you and the cost of the timber and other means to access it, then this becomes less interesting.
In energy terms, if you compare with the heat loss through the walls and other means, then you realise that the focus should be on other issues than this.
.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No, I can't, you do them

Ta
one episode of tripping over a pipe and putting a foot through the ceiling will take a hell of a time to balance against the extra 8" insulation.
mike r
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Put counter joists in to make it deeper for more insulation and board over.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 14/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Why? In comparison to everything else, it's little more than a drop in the bucket.

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Not so. read other post.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 13/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Consider using Kingspan or Celotex. Although more expensive that rockwool, 100mm will give a lot more insulation that rockwool. It is also longer lasting and less prone to sagging and soaking, as it comes in solid blocks looking a bit like expanded polystyrene. You can board straight over the top.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Best put Rockwool up to joist height then lay Kingspan over then loft boards.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 13/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Which doesn't give the OP his required boarded area. If he was going to cover the boards, he might as well use rockwool, as it is better pricewise for the same u-Value.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I think you misunderstood. Best put Rockwool up to joist height then lay Kingspan over the joists, this prevents thermal bridging via the joists. Then loft boards over the Kingspan. Only the part of the loft where you can walk is worth boarding, unless all the loft is used for storage.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 13/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Wouldn't the boards get quite squashed where they lay on the joists? Obviously, crosslaying is the best solution. However, if the OP is only going to fit stuff between the joists, it may as well be Kingspan than rockwool.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Many ways in which to get around that. I think Kingspan do a board which mean for floating floors so this can be used, or you can always counter baton with baton the thickness of the Kingspan and put boards over that.

That is true, but There will be lost of waste with Kingspan, unless you path it all in and the remainder scatter around the loft in places that nothing is stored or walked on.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 13/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Laying over the joists and taping up the joins will add it air-tightness too.
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 13/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

How mixed up you are. Overall the walls loose more heat than the upper ceilingof a house. That is misleading. Then look at the individual rooms below the loft. They will have a large area which is loft ceiling. Then it makes sense to heavily insulate, as these rooms will be warm in winter and cool in summer. In August the coolest place in my house was the main bedroom. No heat came down from the loft above as I have 350mm of insulation. A light wind through the two windows and it was fine in the upper rooms. In winter they are very warm.
And you said a uni made you think?
--
--

Checked by AVG anti-virus system (http://www.grisoft.com ).
Version: 6.0.561 / Virus Database: 353 - Release Date: 14/01/2004
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Obviously. The area is generally larger and the U value greater or comparable to 100mm of loft insulation

They will have a large area of walls and windows as well.

That doesn't follow at all.

That doesn't follow either.
Provide the dimensions of the room including the windows and the construction type of the walls and windows and we can do the sums.
I would be very surprised if the difference in heat gain that you experience through having 350mm of insulation vs. 100 or 150mm is significant in comparison to gains through other surfaces.

.andy
To email, substitute .nospam with .gl
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.