rsimon

Oh! I wasn't aware of that. The foam itself is closed cell and not breathable isn't it?

Hi @joth yes agree, hence the approach mentioned above. Although I still worry about a couple of internal walls that used to be external and hence have cavities. No way we can fill these! The firm that came and had a look at the insulation removal has quoted just over £5k for it. Filling all cavities with the liquid foam comes to around £8k.

We are thinking of using an a liquid foam that they pour into the cavities that slowly expands to fill the cavities. Hence the steps to try and remove the batt insulation. Its a detached house, was a bungalow built in the 60s, but gradually extended on either side over time, as recent as the early 2000s so not has most of the cavity walls empty except the newer side where there is batt insulation. The PH consultant has said that we need to fill the cavity first (for airtightness) then do EWI. The roof is a standard timber joist roof, concrete tiles (!?). We have planning and within it we have mentioned EWI etc. Local authority is happy.

Hi @Gus Potter, thanks for the comment. Reducing carbon foot print is important to us and at the moment we're only simply thinking in terms of enhanced comfort not just for us but also for anyone living in the property in future. Also doing our bit for the environment for the next gen. I feel that if we do piecemeal, it will put us in a position of not really knowing if it's made any real difference at all. This is one of the reasons for choosing to do Enerphit both in terms of methodically approaching it and also having a standard to meet that we can use to measurable value added. Hi @ToughButterCup, will check it out, thanks. Hi @Dave Jones, yes, VAT is certainly one of the considerations. And we do hope to stay here for a while. Hi @joth, thanks for the comments and for sharing your experience. We did start off with the intention of doing it in one go but due to some reasons out of our control had to phase it. Airtightness is a key consideration for us primarily in order to get good air quality for health reasons. We did a lot of intrusive work before moving in but appreciate that we have to move out for some time at some point with either option. Four in the family with two kids, and I don't think they would mind the adventure of moving out for a few months if it is guaranteed that they'll come back to a better house. There is an emotional aspect to this as well as there are some retrofit compromises due to the nature of the house which we can potentially get rid of when starting from a clean slate. I do get the very valid point around VAT! Hi @ProDave, Yes, Enerphit specifies 1.0 ACH@50Pa. If we fail the air-tightness test it would be a mental fail/disappointment, but won't have a choice but move on at that point I guess. Badge would be great to have though. And I don't think energy savings alone will pay for any of this. At least not in our lifetime. One of my frustrations is contractors, especially for retrofitting to a standard. No one I have come across has any clue on what I am taking about and always try to convince me that it's a waste of time. Really tired with that process and also do not have the time to be around all the time to track quality of work. I don't know if this is a general problem. At least with a new build I can hand this over to a specialist and step back. Hi @Iceverge, our current air-tightness approach is external with a parge coat (using the EWI adhesive) as you have rightly suggested, but the purple paint is an interesting option. I'll certainly check it out. Another frustration is that our current approach specifies that we fill the cavities to really guarantee airtightness and I found out recently that there is batt insulation in some of the walls which requires specialists to get it out. I'm not sure if this is a must if the purple paint is used. Do empty cavities contribute to air leakage? The roof is also going to be warm with the approach you have mentioned with an airtight OSB deck. Hi @MikeGrahamT21, thanks for the observation and input. Very valid indeed. I've heard the same from some family members as well but however mad the idea is, I just want to do a proper comparison and assessment and then discount the idea if it doesn't make sense.

Hi all, We've been slowly doing a retrofit over the past two years or so with the aim to get Enerphit certification. We have done a PHPP with the help of a passive house designer. Current status is this: half of the windows and the front door have been replaced with passive certified components. We have an MVHR installed (hard work retrofitting this, but it is in). We've just put in a new kitchen, done three bathrooms. We plan to rebuild the upstairs, replace the rest of the windows, replace the roof with insulation etc. We will certainly struggle with air-tightness. While doing all this, I am now wondering if it makes sense to continue this further, or knock down the house and rebuild from scratch as a fully certified passive house, perhaps using ICF for speed of construction. I'm trying to build a business case for this with the following approach: - We use the current windows and front door in the new plan. - We use most of the components in the three bathrooms we have just done up including shower trays, glass partitions, toilets, furniture etc. - We use the new kitchen and appliances we have just put in. - We use the MVHR unit but redo the ducts in the new house. - We save money with reduced energy bills over say 15 years, compared to the current house or even become net zero positive with solar. - We are planning to rebuild the upstairs anyway as per the current plan with a new insulated roof and replace the rest of the windows in the house. So is it just the new foundations and the ground floor structure and finishings that'll be extra? With the above approach, does it make sense to think about a knock down a rebuild, which will give us a better house without the retrofit related compromises? Obviously there will be costs associated with demolition etc. I'm not sure how to begin analysing this. Has anyone done anything like this or can provide some useful nuggets to ponder? Any thoughts will be much appreciated. Thank you.