# Cavity block house - Avoid?



## Sinto99 (28 May 2012)

Hi,

I am currently very interested in buying a house in North Co Dublin but have just found out that it was built using 9" cavity blocks and then drylined inside.

The estate agent says the house was built approx 25 years ago and apparently using 9" cavity blocks was still very popular in Dublin up to quite recently (which I was very surprised at)

There is no evidence of moisture crossing the cavity block to the inside ot the house but how can you be sure without pulling the dry lining off?

I would be worried about being able to keep the house warm, is this a real issue for cavity block built houses?

I know you can get internal insutlation fitted but this decreases room size and costs €'s and you can get external insulation done but this cost €€€'s

Should I avoid this type of house altogether? I think alot of the houses in the area I am looking at have this type of construction.

Any help/advise would be appreciated!


----------



## lowCO2design (28 May 2012)

EWI would be better if increasing insulation levels in a hollow block house


----------



## Guns N Roses (28 May 2012)

Ask the estate agent for the BER cert. All sellers have to provide one. It will tell you how energy efficient the house is.

As a general rule of thumb, the older the house is the less energy efficent it is.


----------



## Sinto99 (28 May 2012)

I have asked the EA for the BER and the report so just waiting on them to come back to me (she wasnt sure but thought it was a cat D)

Im just looking to see if people had been in similar situations with their own house and wish they had stayed away from a cavity block house altogether, or is it a case of these houses are fine aslong as they are looked after and keep and eye out for mould/cold spots.

From what I have researched on the net it does seem that exterior insulation does give the best result but it is very expensive and my budget wouldnt stretch even with the grant.

If I was to go for the internal insulation option should I pull down the existing dry lining and battons and stick the new insulated board directly to the wall or just leave the existing drylining where it is and stick/nail the new insulation board to it?


----------



## Guns N Roses (28 May 2012)

Sinto99 said:


> If I was to go for the internal insulation option should I pull down the existing dry lining and battons and stick the new insulated board directly to the wall or just leave the existing drylining where it is and stick/nail the new insulation board to it?


 
If you pull down the drylining and fixing the insulation directly to the wall option, it is likely that you will have to fit a new damp proof membrane between the wall and new insulation board.

Bear in mind that the drylining option will not be as effective as the external insulation option. It will also be more messy if you are planing to live in the property during the renovations.


----------



## Sinto99 (28 May 2012)

Thanks for info and advise. To be honest I would put up with the mess during renovations if it meant I could save some money, as I say, I think the external insulation would be out of my budget.

I was thinking of taking down the old battons & plasterboard & sticking the new insulated boards directly to the wall so that it doesnt impact on the roomsize as much but hadnt thought about having to fit a DPM

Again, thanks for the info and advise, all appreciated


----------



## lowCO2design (28 May 2012)

IMO hollow block was never designed to have insulation inside it. 


you cant hang pictures,
you cant have the required thickness of insulation due to interstitial condensation,
you loose the benefit of the blocks thermal mass,
you still have thermal bridges because of internal walls, floor and ceiling and
you reduce the floor area of the house, probably by more of a loss in resale msq space cost than that of ewi
+ the disruption and redecorating time & money of having internal work of this nature done - think skirting, rads, ceilings, sockets etc
negotiate with the vendor to allow budget for EWI (BTW i'm not an ewi rep its just proven as the best method of insulating a hollow block house)


----------



## hastalavista (28 May 2012)

Guns N Roses said:


> If you pull down the drylining and fixing the insulation directly to the wall option, _it is likely that you will have to fit a new damp proof membrane between the wall and new insulation board_.



where and why and is this suggestion insulation independent?

OP is it a semi d? if so how will you liaise with neighbors?


----------



## Guns N Roses (28 May 2012)

hastalavista said:


> where and why and is this suggestion insulation independent?
> 
> OP is it a semi d? if so how will you liaise with neighbors?


 
The OP asked if they could remove the original drylining and apply insulation board directly to cavity block construction. Considering the age of this house I would expect that the drylining would consist of plasterboard fixed to the wall with treated timber battens with some form of damp proof membrane either behind the plasterboard or between the battens and the wall. The OP may damage the damp proofing when there are ripping of the drylining. If they are going to apply insulation directly to the cavity block then they are going to have *to prevent dampness* travelling through the cavity blocks to the interior.

Hastalavista, you can rest assured that my advice is independent. The OP should employ an Architect to carry out a survey and to advise them before purchasing.

As lowCO2design said the external insulation option will be the most effective. It should eliminate all termal bridges. The drylining option *will not.* The OP should spend the money now and save in the long term with lower heating bills. If the OP can't find the extra money for decent insulation then I question whether they can afford the house at all. Maybe they should look elsewhere.


----------



## hastalavista (28 May 2012)

Fair enough with the reply: just to look at it again



Guns N Roses said:


> If you pull down the drylining and fixing the insulation directly to the wall option, it is likely that you will have to fit a new damp proof membrane between the wall and new insulation board.
> .



It was not clear from the above where the new dpm was going to go.

However from your more recent post it seems the dpm is to stop damp from outside passing through hollow block into insulation.

The concern here is that if sufficient insulation is fitted inside the dpm, then the dew point (for the moist air permeating through the dry-lining) will be on the inner face of the dpc and cause endless problems with mould etc.

The general consensus in this arena is that no more than 1/3 of the total wall insulation u-value should be on the warm side of the dpm. The underline is to highlight that its the U value that is 1/3: 2/3, and not the thickness if the materials on both sides of the dpm are different and hence different U values

There are  insulation materials available which will address the problem of wall side damp.

Hope this helps
ps never any suggestion that u had an agenda: sorry if I gave that impression

ps: agree that ewi, if done right, is the way to go


----------



## ladybird (28 May 2012)

On a non technical basis, i grew up in such a house. They are cold and damp and mould appears regardless of you watching for it. We used dehumidiifers in the 80s and two of my siblings have long-term illnesses related to this atmosphere. 

So, please, please think carefully. Ours was a 70s build. My mother had it externally insulated a few years ago at great cost (can't get her to leave the blasted thing). It was the best thing ever. 

Also, do you want to have to come home every evening and every weekend and think - i have to get stuck in at this now (internal insulation). It can put huge strain on a relationship and take time away from your kids growing up. An 80s house will still need a lot of maintenance and jobs done and you might add in the cost of rewiring and plumbing to the internal insulation job as you'll have to sort all of it now as it makes financial sense to sort it now.

You only get one life...there are loads of houses..... but all the best whatever you choose

Ladybird


----------



## Lak (30 May 2012)

Internal insulation on most property types is an excellent way of insulasting a home. On cavity block construction it most certainly IS NOT.
Without getting technical, this type of insulation encourages mould growth, and more to the point mould growth that is extremely dangerous to ones health.
There are methods which can overcome the problems and include using a DPM (damp proof membrane)  and not a DPC (damp proof course ) as someone mentioned... this said it is an expensive method and one which would be on par with externally insulating.
All said and done DO NOT coinsider buying a property of this type if you intend to dryline in therma board, if you value your health. I am sure you will find one of a number of reports through Google that will testify to this.
Contact SEIA Ireland and ask their advice if you want their opinions.


----------



## hastalavista (31 May 2012)

For folks who want to read more about internal insulation and mould see these search results
Joe Little is a world expert on this in the Irish context. Ireland is much damper than the rest of Europe.


----------



## RiceCakes (5 Sep 2012)

If you were to insulate a cavity block house externally and you suspected existing mould behind the dry lining, would it be a massive expensive job to remove all the current dry lining and plaster over the cavity blocks at the same time as externally insulating - would that prevent mould reoccurance once and for all? 
If that was too expensive how long roughly would the mould hang around if the house was just externally insulated and the internal dry lining left, or would there be forever be a musty smell?


----------



## ladybird (6 Sep 2012)

Ricecakes, someone technical will no doubt be around soon but can i just say that smells are particulate - so if a house smells mouldy  - you and your family are inhaling mould spores 24/7. 

Please google health risks of long term exposure to mould and see the damage it does.

Musty is different i think - more stale air from lack of circulation/ventilation/heating - i'm sure someone will correct me if i'm wrong....

Ladybird


----------

