Attic Insulation - A couple of questions

Canaboid

I've moved into an old semi D with bugger all attic insulation so it's going to be an itchy weekend for me.

Does anyone have recommendations for the best type of insulation to use and where to get it a a reasonable price (south Dublin).

Any other tips on installing are greatly appreciated.

noby

If you're using the rolls of fibreglass insulation, cut the rolls to the width of your ceiling joists. Any old saw should do it. Then when you roll them out, they'll fit snugly between the joists. Oh, and be sure to leave a gap at the end for ventilation at the eaves.

CJhaughey

Rockwool is way less itchy than the fibreglass.
I used a long knife to cut it which didn't make as much dust as the saw.
the saw will be wrecked very quick cutting the insulation so get a cheap one if you use this method.
Get a "noddy suit" one of those disposable overalls that cost €5-00 each and wear it.
At the same time get a moldex dustmask they are great and will stop you hacking and itchy throat.
and one more thing a pair of long gloves -marigolds etc worn under the suit.
away ye go!!

Canaboid

Thanks guys. Is there a difference in price/effectiveness between rock wool and fibreglass ?
Any ideas on the best place to get this, I'm thinking B&Q/Atlantic is there likely to be cheaper available ?

CJhaughey

Rockwool is more expensive, try Capco CPD they can give good prices.

fintan

If you want to a greener solution try something like thermo hemp

http://www.ecologicalbuildingsystems.com/products/thermohemp/

It does cost a little more than rockwool, but has won awards plenty of awards and is 100% pollution free.

There are other people making insulation from hemp, so shop around

Muggins

Any recommendations on where to buy the ThermoHemp in the vicinity of Cork city ?

fintan

First place you should look muggins is the Sustainable directory

http://www.sustainable.ie/directory/index.php

Muggins

I checked the link but could find any info on Thermo hemp. I also googled around but can't find any Irish based info. Any leads would be appreciated.

Victor

Do not insulate without thinking things through properly or you could end up with a rooted roof from condensation. Make sure the attic is properly ventilated.

fintan

Sorry the link was of no use to you

www.ecologicalbuildingsystems.com is the Irish company behind thermohemp give them a call, Im sure they can arrange samples and delivery to Cork

KAGY

I'd us a garden shears to cut insulation
In the current building regs (which don't actually apply to 2nd hand houses unless you're modifiying them) they suggest 150mm fibreglass or equivelent between the joists and min 100mm across them.
If you have a header tank in the attic you should remove any insulation from under it to stop it freezing in the winter, but insulate around and above it. You could use 100mm expanded ps to make a box from the ceiling level up, over and around it.
One small point about place insulation across the rafters is that you will have difficulty walking on them, it is suggested that you provide some form of walkway to the header tank
And don't forget to leave a gap where the roof meets the wall to allow ventilation and prevent condensation rotting your timbers.
Karl

GreeBo

Hmm I have the attic insulated between the rafters and then most of the floor area is floored with the usual chipboard.
I wasnt aware that laying across the rafters was also advised.
Doesnt that kinda render your attic useless?

Victor

KAGY wrote:

One small point about place insulation across the rafters is that you will have difficulty walking on them, it is suggested that you provide some form of walkway to the header tank

You are thinking of joists. Joists are horizontal, rafters slope.

GreeBo wrote:

Doesnt that kinda render your attic useless?

Depends on what you want your attic for. Some attics are too small for storage.

Sleipnir

Hullo,

with the recent temps I have also decided that I need to reinsulate.
At the moment there is no insulation on the roof at all (just the floor of the attic) so I definately need to do that.

Also, the dirt up there is unbelieveable (i.e. you can't move anything without a being smothered in a cloud of dust) so I was wondering if it would be a good idea to put plastic sheeting on the inside of the roof tiles between the rafters, then insulate and then cover with marine ply? Or would this this screw up the ventilation?

Does anyone know how much that hemp is per sqm/sqf?

Victor

That sounds like the perfect plan to ROT your roof.

You need a vapour barrier on the warm side of the insulation, not the cold side.

rooferPete

Sleipnir wrote:

Hullo,

with the recent temps I have also decided that I need to re insulate.
At the moment there is no insulation on the roof at all (just the floor of the attic) so I definitely need to do that.

Also, the dirt up there is unbelievable (i.e. you can't move anything without a being smothered in a cloud of dust) so I was wondering if it would be a good idea to put plastic sheeting on the inside of the roof tiles between the rafters, then insulate and then cover with marine ply? Or would this this screw up the ventilation?

Does anyone know how much that hemp is per sqm/sqf?

Hi,

Do I understand that by "The Floor of the attic" you mean on top of the ceiling between the joists ?

The only reason you should have for fitting insulation at the roof level between the rafters or even directly under the rafters is if you are converting the attic to a room.

A good level of insulation would be 200 mm laid between the ceiling joists but not actually touching the roof, if you have 100 mm of insulation already a good investment would be to fit another layer of 100 mm insulation on top of the existing making sure to taper the ends where it meets the roof and tack the insulation to the trap door.

In practice when you open the attic trap door (especially in this weather) it should be like leaving a warm room and stepping outside the house, a good through flow of air is vital in the attic to protect your timbers from condensation which in turn can lead to the timbers rotting.

What you can see or feel is very often not the true enemy, remember the rafters and all the other roof timbers are usually fixed with standard nails which will rust very quickly if subjected to continuous moisture from any source.

I know the argument can be made for roof trusses that are fixed together using plates made from galvanised steel, but the plates are rarely if ever treated individually so every edge and each hole made to achieve the teeth (nails) in the plate can be a good candidate for rust.

As advised by Karl,

Ensure the insulation does not travel under any water storage tanks but insulate around the tanks using a method like the box he described.

Even use duct tape to hold a layer of insulation in place around the tanks and make sure to insulate any pipes in the attic including any expansion pipes.

.

iandromiskin

This may sound like an odd question, but which is the hot side of the insulation and which is the cold side, how do you tell ??

I know you were talking about blue plastic - first of all why blue ? And can you cut it to size and lay it between your ceiling joists and lay the insulation above it ? That way at least the wood is not covered and shouldn't rot ????

Ian

Victor

iandromiskin wrote:

This may sound like an odd question, but which is the hot side of the insulation and which is the cold side, how do you tell ??

The hot side is the side with the vapour barrier.

mukki

no point starting a new thread,

the mother in laws house has about 2 inches of the white foam balls (the stuff used in cavity walls) sprayed all over the attic, i was thinking of replacing this with fiberglass, ir maybe jusr covering it

is the white foam balls any use
and is is safe to leave it there

edanto

4 years later, and along comes me with the same question as the fella above! Any point getting rid of those little balls or is it better just to lay some new insulation over 'em?

random.stranger

Assuming those foam balls are polystyrene, they can have a chemical reaction with pvc coated electric cables over time.

See page 12: http://www.seai.ie/uploadedfiles/InfoCentre/Insulatingyourhome.pdf

Electrical wiring
Polystyrene insulation should not be placed in contact with
PVC-coated electrical wiring, otherwise the PVC may degrade.
Also, steps should be taken to ensure that any electrical wiring
covered by the insulation does not overheat.

Granted, this is in the wall insulation section, but the same principal applies to attic imo

khm2008

Sleipnir wrote: »

Hullo,

with the recent temps I have also decided that I need to reinsulate.
At the moment there is no insulation on the roof at all (just the floor of the attic) so I definately need to do that.

Also, the dirt up there is unbelieveable (i.e. you can't move anything without a being smothered in a cloud of dust) so I was wondering if it would be a good idea to put plastic sheeting on the inside of the roof tiles between the rafters, then insulate and then cover with marine ply? Or would this this screw up the ventilation?

Does anyone know how much that hemp is per sqm/sqf?

Dont put plastic om the rafters youl just cause them to sweat and rot you can put rock/fiberwool inbtween the rafers aswell you can use spikes with a sticky end cant remember woth there called there used to put installation behind cladding or with lats put across the rafters to hold it inplace and for the floor put the installation under the ply its a better job, if you dont want to pull up all the ply take up some in random spots and then push the rock/fiberwool under just be careful of wires for lights
hope this helps

megafan

CJhaughey wrote: »

Rockwool is way less itchy than the fibreglass.
I used a long knife to cut it which didn't make as much dust as the saw.
the saw will be wrecked very quick cutting the insulation so get a cheap one if you use this method.
Get a "noddy suit" one of those disposable overalls that cost €5-00 each and wear it.
At the same time get a moldex dustmask they are great and will stop you hacking and itchy throat.
and one more thing a pair of long gloves -marigolds etc worn under the suit.
away ye go!!

Jeeeuss I'm feeling itchy just reading this post!! Good Luck!!

Murphj7

I have the attic insulated recently. I want to put a few walkways around the attic. What would the best measurement between insulation and chipboard for the walkway?

GreeBo

Murphj7 wrote: »

I have the attic insulated recently. I want to put a few walkways around the attic. What would the best measurement between insulation and chipboard for the walkway?

You dont need a gap, just dont compress the insulation.
If its rigid insulation you dont need to worry about it, if its rockwool etc then just dont compress it and you are fine, you dont need a gap.

bungaro79

how deep should the insulation be?? we've the type that is loose up in our attic. and from reading above, should i not be putting boards across the joists for storage??

Pudzianowski

300mm should be fine, 2 layers of 150mm

GreeBo

bungaro79 wrote: »

how deep should the insulation be?? we've the type that is loose up in our attic. and from reading above, should i not be putting boards across the joists for storage??

if your insulation is above the level of the rafters you can raise the rafters (with more wood) or you can buy clip on plastic lifts designed to put flooring on top (B&Q have them for example)

bungaro79

thanks lads, think its a bit shallow in places so might look into getting it topped up