Spray foam in attic and differing recommendations

Lots of questions rolled into one, but I will do my best to help you out :P And yes, I do work in this industry Are there differences in the foams, Yes. The Biofoam NSAI cert states that it has a C-2 fire rating, which means that in the event of a fire, it will release varying levels of smoke. The E-zero cert gives it a B-2 rating, meaning that there is no smoke released, thus making it far safer in that regard. Both foam certs state that they must install a breather membrane prior to the installation of the foam itself, which means that the membrane itself must be breathable. This means that if you hold it up to the light, you should be able to see light through it. I would seek verification of this prior to works. If you can not see light, it is not breathable. You should also note that unless these contractors have a very good reason for installing 125mm of foam, they should be installing 150mm to meet current regulations.

In relation to the front porch, that really depends on if this is a heated area of the house. If it is not, then you will not gain anything from insulating it, however if you have a bay window that has a separate roof, it should be insulated, as this is an area that will allow cold air into your living space.

I'm not sure that I understand the position on the walls. Are you thinking of filling part, or all of the walls? Is it a normal cavity or are there cavity blocks in play? You mentioned dry lining a couple of rooms which makes me think that there are cavity blocks in the construction. It is not a good idea to part fill a wall, as the section filled can cause an area for moisture bridging within the cavity. Maybe I did not understand properly

It can be a bit confusing as there are contractors out there that treat the regulations as something that can be manipulated to suit their needs depending on the job at hand, but regulations are there for a reason, and I would advise making sure that the company you select, respect and adhere to these regulations, as they are in place to safeguard you and your property.:)

Snabe wrote: »

thanks for the reply

yeah there is brickwork on the bottom front half of the house,so we'd be injecting the bead into there. the top half of the front of the house wouldn't be having anything done to it as it's not brickwork. is there any point in insulating the bottom half of the front of the house like this?

we're only going to dry line our baby's bedroom at the back of the house as it has two exterior walls and is impossible to keep warm in winter. we were putting her to bed last winter in vests babygros and cardigans, her room was freezing.

Hi again Snabe. Could you just clarify why it is that you are only looking at the bottom section of the wall. Is it the case that the rest of the construction is cavity block, or is there a standard cavity? If it is a standard cavity, then there is no reason why the whole wall should not be done, but if it is cavity block (9" cavity blocks), then it is not advisable to fill. The previous companies that carried out the surveys should have given you this information already. Its just that the information that i'm gleaning from your previous messages are confusing. If you are looking at dry lining a couple of rooms, this obviously means that they have not been previously lined, which would be standard practice if you had a 9" cavity block as part of the construction. This being the case, i return to my previous query, why attempt to part fill the wall?
Its just that it can be difficult to give accurate information without understanding all of the elements in play.

The answer to "Is it worth doing the roof and gables", absolutely, but if the attic has been converted already, you need to be sure of how they intend to approach the installation. I would assume that you currently have some form of insulation installed in the attic. This would have been done during the conversion. You need to know what type of insulation is currently in place, particularly in the sloped section, ie. fibrewool or rigid board, and are the installers going to remove this prior to spraying? Also, is the felt a breathable or black bitumen type felt?

Spray foam insulation is superb for making your roof draught proof, but you MUST have the appropriate moisture controls in place when using foam. Do not let your installer take short cuts, as it is you that will ultimately pay for it. It could also explain why you obtained the differences in the quotes. :eek:

Muddlingthru wrote: »

Eire sun, I have a converted attic in a 1950 s house, semi d. We are losing huge heat through the roof. At the bottom of the eaves we have presses, so I can see what is there is like rolled out fluffy stuff which is then lined with plywood, but there are gaps at the bottom so gale force winds blowing through.

Above the presses, the roof is lined with plasterboard and I assume the same insulation is in there.

Can attic roofs be spray foamed from outside or is it all done from inside and how?

Any suggestions welcome, and your contact details if y are in the business.

Also interested in insulating cavity walls. Next door up for sale so it's possible new occupants might go with us on exterior insulation. Any views on this?

Thank you!

Hi Muddling,

Yes indeed, it is possible to insulate a roof of this nature, but there would need to be access made to reach the crawl spaces at the bottom, or eaves of the roof. The method remains the same as would be the case with any type of roof structure, the original insulation would need to be removed from the slopes, a breather membrane fitted to run from the wall plate level to ridge level, and then open cell foam installed via spray and cannoning techniques.

However it should be noted that in this particular case there is one factor that is beyond the control of any installer, and that is the rafter depth. It is not an issue in the crawl space and apex areas, however on the slopes you would still have an airtight seal, but you may not quite get the u-value that would be desired. This could only be determined during a survey of the roof.

I hope this helps a little. If you need any more info please feel free to pm me.