Internal insulation for home with very large windows.

Confused11811 · 11-05-2021 3:26pm #1

Hi folks, I'm hoping to get some renovation work in my home soon, new heating system, flat roof repair/replacement on converted garage, rewiring and changing some of the internal layout. I'd like to add some insulation too, Attic will be done, I'll probably do the subfloor too.

I'd like to add some internal insulation on the cold external facing walls where in one or two rooms wall condensation can be found in winter, currently there is no form insulation on the walls with condensation. However the windows are huge in my home and I'm unsure what the best sort of insulation option would be. I'm not too keen on the current windows, I think the ones in the rear of my house may have been fitted incorrectly as they do get a lot of mould around them so I'll probably replace the lot. I'm considering reducing the window width by a block, getting new windows and insulation on the current cold external facing walls. I'd have to get the external walls dashed to which would add to expense (possible planning issue??)

However if properly fitted new windows remaining same size as the current ones and insulation can address winter condensation and mould I'd be happy to go with this. I actually find the house warm as is so really looking for the most cost affective option to get rid of condensation and mould, feedback would be appreciated.

The current vents are clear with no obstructions but if better ventilation could address the problem I'd appreciate feedback on that too.

PMBC · 11-05-2021 3:43pm

Looks like cold bridging at the window reveals

Confused11811 · 11-05-2021 4:23pm

PMBC wrote: »

Looks like cold bridging at the window reveals

I suspected the rear windows which are different to the front where a DIY job from the previous owner. I think they where put in without an insulted material around the window reveal. I assume properly fitted new windows could address the issue ?

MicktheMan · 11-05-2021 11:50pm

Confused11811 wrote: »

I'd like to add some internal insulation on the cold external facing walls where in one or two rooms wall condensation can be found in winter,

This is not a good idea and increases the risk of making the condensation situation worse except this time it will be hidden. What is the makeup of your external walls? Is cavity or external insulation an option? Imo, IWI should only ever be a last resort and only then with special consideration to the product used as well as other critical mitigation measures such as excellent ventilation.

10-10-20 · 12-05-2021 2:16pm

Looks to be a later 1960's/ early 1970's build. Most likely cavity-block.
Can you strip a reveal or drill a reasonably sized pilot into it to check the make-up of the reveal?

Confused11811 · 12-05-2021 3:18pm

Sorry I meant to reply easier. @ 10-10-20 your bang on the money, it's an estate from 1969/70 with traditional cavity-block. I cleaned out the air vent a couple of months back which did make a difference regarding the condensation (condensation only happens in one room, the master beedroom), that room is just plaster over the brick, no slab that I could see. I checked all the other vents at the time and they appear to have had a 15-20 mm installation board between brick and plaster, I assume this was added by the previous owner at a later time. The bedroom with the mould around the window has received the same 15-20mm insulation board.

Master bedroom

Master bedroom

Room with Mould

Calahonda52 · 12-05-2021 3:21pm

did the reveal in the "The bedroom with the mould around the window has received the same 15-20mm insulation board." get insulation on the reveal?

Confused11811 · 12-05-2021 3:41pm

Calahonda52 wrote: »

did the reveal in the "The bedroom with the mould around the window has received the same 15-20mm insulation board." get insulation on the reveal?

From the small hole I just bored out it looks to me like the windows where put in and about 20mm of plaster around the reveals.

Gumbo · 12-05-2021 4:51pm

Are you changing the windows?

Dudda · 12-05-2021 5:03pm

Would you consider external insulation? If replacing the windows and externally insulating you can reduce the window size if required. In addition you can move the window further out so it's on the same plane as the external insulation. This helps with thermal bridge and cold spots around the windows. External insulation would be more expensive but grants are available and you won't lose internal area. You can also add lots more insulation like 150 or 200mm. It sounds like you're planning a lot of work (rewire, attic insulation, roof to garage, windows, potential subfloor) so may as well do it all and do it right.
You may need planning if you're changing the size of the windows not the style. If the window size stays the same you can change the windows and add the external insulation without planning. They can add dash or fake brick slips to the front so it matches the neighbours so that's not an issue.

Confused11811 · 12-05-2021 6:05pm

Gumbo wrote: »

Are you changing the windows?

If it's the most cost effective way of dealing with the issue I will, I'm not a fan of the brown windows. I rather white/cream or maybe that light grey that everybody seems to be going for lately. I know some PVC windows can be painted/resprayed but I'm not sure on the durability and cost of doing so along with the cost of addressing the cold bridging would make it not worth doing

Dudda wrote: »

Would you consider external insulation? If replacing the windows and externally insulating you can reduce the window size if required. In addition you can move the window further out so it's on the same plane as the external insulation. This helps with thermal bridge and cold spots around the windows. External insulation would be more expensive but grants are available and you won't lose internal area. You can also add lots more insulation like 150 or 200mm. It sounds like you're planning a lot of work (rewire, attic insulation, roof to garage, windows, potential subfloor) so may as well do it all and do it right.
You may need planning if you're changing the size of the windows not the style. If the window size stays the same you can change the windows and add the external insulation without planning. They can add dash or fake brick slips to the front so it matches the neighbours so that's not an issue.

I'm considering my options as to the best course of action to address the mould/condensation/insulation but at the same time I'd like to be as cost affective as possible. I'm not overly concerned about getting a top end BER rating, rather just getting the house up to good modern standard which could be comfortable while addressing the issues.

I'm not really concerned about PP for window size changes, I've look around and its been done on other homes in the estate which have had the external insulation added that you describe. I also have active PP for build plans which I now won't be going ahead with due to a change in my own plans with those but those plans did involve building above the garage and changing current window sizes else where. I'd be happy to apply for retention if required after the fact bases on the above, but I doubt it would.

I've no experience in applying for grants but from some family members experience they found grants could slow things down and can add a large percentage cost to compared to say dealing with cash. How true that is I don't know, any input would be welcome

Resizing the windows would give me the option of running full length fitted wardrobes across all bedrooms so for future proofing that would be a positive be it's not crucial. Reducing the internal room size by using internal insulation wouldn't be a major blow either.

I know it's a how long is a piece of string question but would you have any idea on the much of difference of cost of doing internal insulation against the probably better solution of doing eternal insulation ?

Calahonda52 · 12-05-2021 6:48pm

Iff the walls of the bedroom are dry lined and not the reveals then it is not surprising that you have mould on the reveals as that is now colder than the rest of the walls in the room/house so ideal for condensation .
EWI might be problematic with the massive thermal bridge from the concrete roof on the garage

Confused11811 · 12-05-2021 6:56pm

Calahonda52 wrote: »

Iff the walls of the bedroom are dry lined and not the reveals then it is not surprising that you have mould on the reveals as that is now colder than the rest of the walls in the room/house so ideal for condensation .
EWI might be problematic with the massive thermal bridge from the concrete roof on the garage

.

I plan to remove the current roof on the converted garage and raise it. Currently there is a step down , I want everything at the same floor level , to do so required the roof to be raised. It's been done by a number of the neighbors

spaceHopper · 13-05-2021 9:16am

Our house had PCV windows when we bought it. It was freezing. We insulated upstairs and when they opened up the window reveal to do it they found the widows were wedged in with packing, no foam no airtight seal cold air pissing in. Chances are yours are the same.

The widows look old (metal strip in pains) but there should be no reason that can't be used for now. You just need to make sure they are properly installed.

The insulation in the wall now is tiny by today's standard.

Confused11811 · 13-05-2021 9:51am

I'm here 6 years and have had to repair various thing along the line. Each time I found the previous owner work ( he did it himself) while functional was done on the cheap ... a prime example was copper pipes used in the heating where recycled, obvious taken from other houses, different lengths where painted different colours or had wallpaper on them, there was joins where none needed to be. Hats off to him for his eco efforts and it worked but it's a indication that corners where cut elsewhere like the windows.

I always planned to gut the house, but only getting around to it now. I'm getting the impression new windows, properly fitted and maybe upgrading ventilation would address the mould and condensation issues I have in one of 2 rooms. I just need to figure out approx costings on the insulation options and what's the best option for my needs.

Any rough estimates and recommendations would be welcome

10-10-20 · 13-05-2021 10:43am

Skip-diving was more acceptable back then!

With those planned actions on the garage roof, I think you're setting up fine for EWI; retro pebble-dash and all.

Dudda · 13-05-2021 12:14pm

Ya I'd start looking more at the EWI particularly with the planned roof to the garage.

Cost wise it is more expensive than internal but it has advantages:
The house looks new when finished as it's newly rendered and ascetically is a better job
No cold bridges as new windows can be placed in the same plane as the external insulation.
The external insulation can continue up to the insulation in the attic and the new insulation in the garage roof having no thermal bridge
The person installing the insulation does all the grant paper work for you. As its NSAI certified they have to follow certain guidelines so it's good that way. They do put up the cost as it's more paperwork for them but it's still cheaper.
You can seal the windows with airtight tape to both the existing external plaster and internally making sure it's very airtight.
When the works are ongoing you can still live and use all parts of the house as the insulation is added externally. With internal insulation you either move out and then do it all as quickly as possible or they do it room by room so you're living in a building site. With all the other work like rewiring, etc you're probably moving out for a bit so this mightn't be an issue.
You can add as much insulation as you like. A large part of the cost of insulation (internal or external) is labor. The insulation used externally is cheaper EPS while inside it's more expensive PIR as it's thinner and you loose less area. Once you pay for the labor, plaster and scaffolding the difference in overall price of 100mm of external insulation (the minimum to get the grant) and 150mm or 200mm is very little. This is why 4 years ago we added 150mm instead of 100mm. Going back now I'd consider stretching to the 200mm as it's a forever home and in our 30's so will benefit long term.
For window sizes we did reduce one very large window for exactly the reason you mentioned of fitting a wardrobe. Had about 150mm between the wall and window. Reduced it by one block so the 600mm wardrobe fitted.

Internal insulation for home with very large windows.

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