Low cost roof insulation

Furts

Fibreglass or Rockwool rolls of insulation have been available at DIY stores for £5 or less. I need to top up my roof . Homebase are not stocking any roof insulation and Wickes have disposed of all (but for one rather expensive product). B&Q have some but at around £30 a roll - this makes insulating rather expensive!

Has anybody seen any offers during their travels?

brewerdave

If you currently have less than 60mm, most Utility Cos. plus some local Councils will do it for nothing - but the money for this runs out fairly soon.:)

oldskoo1

I have around 170mm - 200mm and was planning on sticking at least another 100mm up there in cross hatched pattern.

Like the op I've checked prices and found it to cost £15-£20 a roll.

Always thought it was a lot cheaper than that. As the benefit decreases the thicker you go there is no point bothering if its going to cost me over £100

rogerblack

oldskoo1 wrote: »

I have around 170mm - 200mm and was planning on sticking at least another 100mm up there in cross hatched pattern.

Like the op I've checked prices and found it to cost £15-£20 a roll.

Always thought it was a lot cheaper than that. As the benefit decreases the thicker you go there is no point bothering if its going to cost me over £100

I question even then.
Assuming that it's properly fitted, and randomly picking an area of 100m^2.
Thermal resistance at 200mm will be 0.02W/m^2/K / .2 = .1W/m^2/K.
For 100m^2, that is 10W/K.
As a comparison, this is the same loss from two square meters of single pane window.

Neglecting the other structure, and assuming an average temperature of 10C across the structure, that's 100W of average heat leak.

Adding another third will take it to 60W, 40W of savings.

This is - if heating with peak rate electricity - about 40 pounds a year.
If using gas, about 10.

Turning the thermostat down .05 degrees or so, or getting the draught sealing around doors/windows properly done will have a far, far greater effect.

Not that all the little savings don't add up - but especially if the walls and floor are not as well insulated - you're going to find it hard to even measure the difference in controlled conditions, never mind the real world.

oldskoo1

Thanks roger

Saved me some cash there, no better money saving measures than that!

I dont have cavity wall insulation, as in my cavities are empty and this is only an 8 year old house.

What i do have is the inner leaf of thermalite blocking and all room partitions are made from the thermalite block too.

I assume that met the correct ratings 8 years back.

I have always questioned wether it is worth filling the cavity, many on my estate have. But i always assumed the savings were very minimal especially as i have the thermalite blocks. I would rather leave them to keep the air flowing and the moisture running down the inside of the bricks.

I know someone with the same house and same heating methods as me who's bills are practically identical.

So on that basis i think i will park the insulation top ups. I've eradicated most drafts now, the only issue is the cold front door and north facing sitting room.

rogerblack

oldskoo1 wrote: »

Thanks roger

Saved me some cash there, no better money saving measures than that!

I dont have cavity wall insulation, as in my cavities are empty and this is only an 8 year old house.

What i do have is the inner leaf of thermalite blocking and all room partitions are made from the thermalite block too.

I assume that met the correct ratings 8 years back. .

Assuming this is so - http://regulations.completepicture.co.uk/pdf/Energy%20Conservation/Best%20Practice%20Guidance%20and%20Case%20Studies/The%20effect%20of%20Building%20Regulations%20(Part%20L1%202002)%20on%20existing%20dwellings.pdf indicates that 0.25W/m^2/K was the limiting value for walls - that must be exceeded.

this is equal to 16cm of fibreglass, or 8cm of kingspan or similar.

Filling a 5cm cavity is going to have a really limited effect, and may have negative effects on the structure.

Wikipedia does reference http://www.eeph.org.uk/uploads/documents/partnership/Building%20Regs%20Compliance%20Report%20Oct%2004.pdf which says that most homes as of 2004 did not meet current regulations.

Furts

To update...I bought Space 170 thick fibreglass at B&Q yesterday at around £15 per roll. Not sure if this was deemed a trade or retail price. Seemed like good value to me - I never found any deals with prices subsidized by the energy companies.

Might be helpful to anyone else looking to insulate their roof?