Insulated plasterboard

TimHorton

https://www.boards.ie/discussion/comment/119926520#Comment_119926520

The "Advice" consists of "Go with EWI and make sure they go 600mm below finished floor Level" and "Get a Heat Loss Survey" , No actual solutions..

https://www.boards.ie/discussion/comment/119927103#Comment_119927103

In fairness, it's almost certainly the correct approach to identify the best solution which will achieve the best outcome. The only problem with achieving the best outcome is that one it usually requires an input of a bucketload of cash. And clearly not everyone has a bucketload of cash available, which in turn leads to requirement for a sub-optimal but good and (critically) an implementable solution which will achieve an outcome which is sub optimal but good or very good.

And yes, it can be clearly demonstrated that a €10k (or whatever sum) investment will pay for itself in the long run, but that's no use to someone who doesn't have the €10k available to them in the first place.

First step is airtightness— a load of insulation is no use if there's a cold breeze coming through.

A practical and affordable piecemeal solution may be foil backed PIR (I'd consider 100mm a minimum) properly taped with foil and then foil backed plasterboard over that placed so the joints on the plasterboard don't align with those of the PIR. Secure the whole lot against the existing insulated PB using mushroom fixings with plastic caps. Tape & seal the joints. You'll also need to do something with any pipes & sockets along the relevant walls. Depending on the age & locations of radiators it's probably worth replacing them with more efficient & smaller ones in a different location.

3x layers of foil should between the PIR and the plasterboard should sufficiently mitigate vapour leakage.

BTW, if your internal walls are block built rather than timber stud, this should give all the thermal mass you need. Even if they are timber stud unless your floor is insulated above the concrete the floor will provide plenty of thermal mass. So I wouldn't be stressing about losing thermal mass.

TimHorton

https://www.boards.ie/discussion/comment/119927218#Comment_119927218

 @ShedHead1 Thanks for that , How have you dealt with Ventilation in your example above ?

https://www.boards.ie/discussion/comment/119941434#Comment_119941434

I have extractor fans connected to the light switches in the two bathrooms upstairs (ducted under insulation via the attic to the gable wall). Leaks in the fabric (which I haven't yet been able to eliminate or properly mitigate) take care of the fresh air coming in.

A centralised Mechanical Ventilation Heat Recovery system would be better when airtightness is maximised. But the system itself cost maybe €2.5k the last time I checked (for a house my size), and I'd need someone to hook it up and there's also a need for ducting from the attic to the ground floor which would be a massive pain.

On the other hand my current arrangement cost less than €200 (including a core drill for the new openings on the gable wall) and works.

MVHR would be significantly better I'd imagine. But including installation, I'd be surprised if I got away with less than €5k (last time I enquired, they wouldn't even give me ballpark figure). The cost benefit analysis just doesn't even come close to making sense as things stand (and is unlikely to anytime soon) so it's just have to go on the list of things that I'll do whenever I have a big whack of cash and nothing better to spend it on....