insulating external walls of old house

Teckie

Hi,

Looking at purchasing an old house that will need insulating, build around 1960's.
Looking at two options:

i) Dryline internally
ii) Pump into cavity if possible, havent been able to check house yet.

Has anyone any idea of approx costs for something like this.

Its a 4 bed semi with converted garage circa 130 sqm

Thanks

Builderfromhell

Techie,
Remember that SEI are offering grants for exteral insulation, dry lining as well as roof and new efficient boiler.
There are loads of companies offering cavity fill insulation so it shouldn't be difficult to get a price.
As for best system, a few photos would help.

Good luck

MicktheMan

Teckie wrote: »

i) Dryline internally

Be very careful ...

My advice, don't do it.

hblock21

MicktheMan wrote: »

Be very careful ...

My advice, don't do it.

Why?

MicktheMan

hblock21 wrote: »

Why?

In general, risk of (interstitial) condensation and mould growth is just too high.

Poor Uncle Tom

Drylining inside is still an option, you just need to know what you are doing and the entire make up of the wall.

Say, you're looking ar 100mm blockwork inner leaf, 60mm board insulation, 40mm clear cavity and 100mm blockwork outer leaf.

If you wish to dryline then the general rule of thumb to prevent interstitial condensation is to insulate inside the wall with no more then half the thickness of insulation which is inside the cavity and ventilate tboth the room space and any dryline supporting timbers.

MicktheMan

Poor Uncle Tom wrote: »

Drylining inside is still an option, you just need to know what you are doing and the entire make up of the wall.

Say, you're looking ar 100mm blockwork inner leaf, 60mm board insulation, 40mm clear cavity and 100mm blockwork outer leaf.

If you wish to dryline then the general rule of thumb to prevent interstitial condensation is to insulate inside the wall with no more then half the thickness of insulation which is inside the cavity and ventilate tboth the room space and any dryline supporting timbers.

P.U.T., you're correct ... on paper.
But the problems arise when
a) the insulation in the cavity is not installed properly and you get thermal looping/cold bridging which negates cavity insulation effectiveness
b) the occupants block up the hole in the wall vents when the cold winter winds blow

sinnerboy

Please expand on the problems Mick

MicktheMan

sinnerboy wrote: »

Please expand on the problems Mick

Condensation / mould

Localised areas (caused by ineffective insulation / coldbridging) where the wall temp behind the internal drylining falls below the dew point of the air. If room vents are blocked/non-existant then the RH rises and the corresponding dew point is higher. The condensate cannot easily dryout and then the mould starts growing behind the drylining.

I just rarely if ever specify internal drylining because the risk of mould is too high. I see it very regularly in houses where scant regard has been given to building regs/ building physics and especially in existing/older (used to be) draughty houses who have had their old windows etc replaced with highly sealed pvc units etc. In no time at all mould appears on clothes, shoes, room corners etc etc not to mention the effect it is having on the building structure itself.

sinnerboy

Ah - but condensation will occur in any house which is not vented .

Dry lining works in practice in 1000's of houses .

Poor Uncle Tom

To get the ventilation element in a house right is very important, but I will not disregard drylining as an option just because someone cannot get another aspect of their building regulations correct. Drylining is a good low cost insulation alternative for older buildings provided ventilation is properly addressed.

MicktheMan

sinnerboy wrote: »

Ah - but condensation will occur in any house which is not vented .

or inadequately heated houses.
Yes SB you're right, to a point, but drylining masks the problem as condensation is at the back of the insulation. But the real problem arises when drylining is applied without any regards to ventilation.
Heres the case I come across regularly. Existing house say 20 years old has never had a condensation/mould problem. Drylining is applied internally and within six months (over the winter) mildew smells start to be noticed in rooms which never had a problem before. Same family/living habits and same ventilation regime. This is the risk I'm speaking of.
Sure, if you test airtightness and make appropriate changes to the ventilation system to account for increased condensation risk then yes drylining can be appropriate but how many "insulation contractors" (SEI registered for the grant) out there know how or have the equipment and training to be able to do such a calculation?