Adding insulation to an uninsulated 1995 conc tile roof, what product and how much is needed?

[difflock]

Hmmm, def no ridge vents, nor indeed soffit vents, so thanks for that "heads up" guys.

Presumably no need, since the roof was uninsulated, and the air circulation within the roofspace void sufficied(it IS proper airy up there!)

But there is a quare draught comes in through the gaps in the overlapped felt, so perhaps little need of furthur ventilation, but better safe than sorry I suppose.

More work, sigh.

Edited March 9 by difflock

[GarethM]

Yeap, vapour barriers only really stop the water. Slows it down but maybe get a roofer to have a look and make a few suggestions, cheap to fit a few vents and a day's work for them 🙂

[Steven P]

I've looked at this for my loft, changing it from a cold loft to a warm loft (or not so cold loft - still keep the installed insulation). I am being put of because no one can really give me a decent answer for the moisture. The actual insulation installation should be an easy DIY job. As far as my thinking goes, don't insulate right up to the tiles, leave a decent air gap there with vents as required. My thinking also to leave a gap along the base of the insulation and at the top / ridge or a vent to allow some air movement between the insulation and the tiles. Before I bite the bullet and do that job I'd get a roofer in for advice (I'm in Scotland, roofs here tend to be tiles fastened to plywood sheets fastened to rafters so more wood that could rot) (other insulation jobs to sort first)

 

 

My loft has more than the minimum required at the moment so was thinking to add maybe 75mm, supported on netting (the orange barrier netting, under the suspended floors is held up with that OK), stapled in place and the insulation placed on top. Loads of space for the spiders to live! Was thinking rockwool as you said about polystyrene, not sure I'd want that burning in the case of a house fire. I did a test once, sheep wool, rock wool, polystyrene and PIR, about the same of each into the fire. PIR and polystyrene loads of black smoke, fire as you'd expect, rockwool just sat there, melted a bit, sheeps wool burnt but no real nasty fumes.

 

We used to get meat packages delivered - meat direct from the farm - and that was insulated with wool, which afterwards was a waste material.. and is now insulating the gable end of the house, it did make a difference I think but because it was filled up over time there was no sudden changes in temperature up there.

 

[carlos]

are trying to warm up the loft or the house?

i find pir board easy to use and you can always use expanding foam for any gaps.

some of the pir board manufactures websites have technical drawings on the use of their products.

i think the extra board on the underside of the rafters is recommended and one could use an insulated plasterboard slab for a more room like appearance although heavier and more expensive obviously.  

[difflock]

Looking to make the house somewhat easier heated, which will indeed make the roof space warmer. If I add the insulation to the rafters instead of the roofspace floor. Which I don't want to do.

We live downstairs, the upstairs is empty, but heat rises and I reckon the extra insulation can only help overall.

[Steven P]

In my case the chimney runs through the loft, the heat transfer, chimney to loft space is above the insulation and this heat goes straight out. Insulate the rafters as well and some of this heat will be retained in the loft, the temperature difference house to loft will be less and the heat loss from the house will be less. So there is some merit to insulate the rafters (as well as the roof space).

 

[Welshfred]

15 hours ago, carlos said:

 

i think the extra board on the underside of the rafters is recommended 

 

It certainly is. Insulating between rafters with airflow above is fine but the rafters then become cold bridges increasing condensation risk. An additional layer of insulation fixed to the underside of the rafters should prevent this.

Regarding airflow, is the roof flat or pitched, if pitched, how steep, single or double?

[difflock]

A traditional pitched roof.

How steep, hmm.

This steep.

Edited March 10 by difflock

[Welshfred]

6 hours ago, difflock said:

A traditional pitched roof.

How steep, hmm.

This steep.

 

Then the recommended ventilation is equiv to 10mm continuous at eaves and equiv 5mm continuous at ridge. You should already have that in your current setup through soffits/ridge vents I'd have thought. Your risk is, if you seal in the rafters there's a risk of condensation. You're getting into vapour control membrane territory too if humid air from the living area can migrate into the boxed in insulation/roof joist space. Suggest further research/professional advice...

[difflock]

No soffit or ridge vents.

N. I. may have had different bld regs to the rest of the U.K. Cos Bld Control did not highlight this lack, though they did mention other stuff, like wrong way round double glazing units. Which, needless to say, are still exactly as they were.

Since we live downstairs, I would have imagined the likelihood of significant  moisture  migrating the length of the roof space was low?

With somewhat poor fitting/ leaky windows throughout the house.

However, to double back on myself Fred, were you suggesting that IF moisture from the living area permeates to the roof space, that the existing non permeable bituminous felt is unsuitable for a warm roof(if that is what it is called) which properly needs the breathable Tyvek type membrane?

But, surely, the provision of the  correct amount of eaves to ridge ventilation negates the need for breathable "felt"?

Cheers,

Mth