70s Bungalow - Possible Gut It - Insulation

[Rogersp]

Hi,

After a few years of looking a building plot in Cheshire, that I could afford, I've now sold my home and have pushed the button purchase an untouched but cared for 1970's bungalow. This will be my last home where I will be carried out in a box!

As I've said the bungalow is almost untouched but think double glazing and central heating were added but both are looking tired along long with the original kitchen. Add to that a poor layout I've decided to more or less gut it and remodel the space, which is mostly all stud work, adding a 4/5 metre extension to the rear to create 7 x 7 metre open living area overlooking a sizable garden.

I've already contacted the Heat Geeks who will do a Heat Loss survey taking into consideration the changes I'm planning which:

• Install ASHP along with larger pipework if required
• Bathrooms
• Kitchen
• Upgrade wiring to include RCBO protection
• Install Triple Glazing
• MVHR system etc., etc

I know, I'm probably going to spend more that the building is worth but managed to purchase the property about £120/130k below similar properties sold in the locality so feel I have funds to play with even if I do over spend.

So, onto my dilemma. I'm still waiting for confirmation if the property has cavity insulation although I'm unable find any filling holes. I suppose i could drill a few holes in the mortar and poke in a camera. Anyway, my question:

If the wall cavities are filled can I still add internal wall insulation, 25 or 50mm PIR, then reboard/skim without an increase risk of interstitial condensation?

Opinions and experiences would be gratefully received

Thank you

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[IGP]

Avoid IWI if at all possible. Fill the cavity if possible (if there is one and not yet filled) with EPS beads. Then EWI. This assumes you’re going to have at least 300mm of loft insulation, and will top up if needed. 
 

To be honest, I wouldn’t bother with IWI anyway unless you’ve got some massive thermal bridges that need avoiding, as you probably won’t get the payback. I’d focus on the efficiency of the heating system, getting the lowest possible flow temperature possible to get the highest SCoP.

 

But that’s just me.

[TommoUK]

..or consider cavity insulation plus external wall insulation and directly applied light weight render system. Harder to detail if you don't have sufficient  eaves/gable projection.

[Rogersp]

Many thanks for your input, really appreciated.

I had considered EWI but the bricks used are really attractive and in exceptional condition so I know from an aesthetical view I know SWMBO would have a fit if I fitted EWI.

The reason I'd dismissed cavity insulation was because of a feature on Skill Builder where Roger B criticised CWI could lead to internal damp etc., so thought IWI would be the best option as long as I would not be at risk interstitial condensation. I suppose I should ask the question, hoiw many people have suffered issues with CWI.

Maybe more research.

Thanks again

 

[SteamyTea]

1 hour ago, Rogersp said:

Skill Builder where Roger B

Don't listen to that tosser, he just likes spouting off.

 

 

[IGP]

I’ve got EPS beads retrofitted in my cavity walls. No issues so far. 
 

I wouldn’t trust blown fibre, as that can have a tendency to snag on the rough edges inside the cavity and cause clumping and then voids behind the clumps. Then you get cold spots. 
 

Beads on the other hand just flow and don’t really care about the rough edges and fill the space. Not only that, they’re not absorbent at all and the spaces allow water to fall through them (eg wind driven rain) and not across them to the internal leaf. 
 

Side benefit - it’s much quieter as sound doesn’t bounce around in the cavity. Didn’t realise about that until a few days after retrofit. 

[IGP]

The videos that convinced me were

 

 

[Markuz]

We have a bungalow project like this and will be doing EWI. We have a filled cavity but no clue how that was done. 
 

I would not  bother with internal wall insulation.  

Our approach is to have a wrap around with Continous insulation (probably around 200mm) to minimise cold bridging and work on our air tightness. 
 

Further more we will be looking at XPS at foundation level which is going to help as well. 
 

Did you check your cavity wall ties? Given the age of house they might not be the best. Reason I am

saying is that you will be adding weight with Ewi so want to make sure it can take it. 

 

[Linto]

Similar project to me. I went with ewi, as it needed a new roof we converted it to a warm roof which allowed us to tie it to the ewi for air tightness and extend all the eaves to achieve this. You can use brick slips on ewi.

We also had cavity wall insulation which had been poorly installed and as we're on the coast was a poor choice but as it's dried out it's an extra boost. 

We also installed new windows. We're slowly insulating under the floors with 100mm rock wool our heating bills are about a 1/3 of when we first moved in. We're still on gas but will be able to easily convert to a heat pump. Now we're slowly doing up the very dated but serviceable inside. 

It's a fun project and keeps me busy.

It's surprising how quiet it is after all the insulation has been done and the kids are asleep.

[IGP]

Also, what’s the floor situation - concrete or suspended timber? 
 

If suspended timber, then there are relatively cheap* insulation opportunities there. Then you get the whole house wrapped up, rather than having a potentially cold floor. 
 

*vs digging up a concrete floor