Abbey,
Your very welcome
Thanks for the kind words
C.
Thanks for the detailed reply, with pictures too!
Very clear to follow for us lay people trying to make sense of the numerous info. sources.
abbey
The present insulation is fine and leave it in place.
I would not use PIR, I would use wool.
Here is a photo of a new flat roof. The wool insulation rolls are on the floor.
Now the wool is fitted between the roof joists in the next photo
Next photo shows the insulated slabs fixed with screws and washers to the joists. You can see the ceiling air/ tightness membrane brought down the walls
This photo shows the roof light with the ceiling slab below - and the edge of the slabs and if you zoom in you can see the insulation and slab.
You said that there are slabs fixed to the inner face of the gable walls. How thick is the insulation on the back of these slabs. If it’s thin, leave it in place and fit new slabs with approx 50 mm insulation over these slabs. First fit an airtight membrane if it’s required.
Regarding the existing ceiling slabs of the dormer rooms. If it is possible to fit the new wool insulation above the slabs from the attic, do not take down the existing slabs. Fix an Airtight membrane if it’s required on to the existing slabs. Then fix the new insulated slabs on over the existing slabs with screws and washers.
Excuse my ignorance.
When you say 'insulate the ceiling with insulation on top of the slabs' are you talking about in the attic.
Currently within the attic there is mineral wool between the joists and some laid on top. It's 15 years old, should it be removed and replace with new wool between the joists and across the joists? Or do we install PIR board between the joists?
We are planning to insulate and draught seal the 4 attic doors in the 2 dormer rooms as you suggested. Is there a particular type of insulation that we should stick to the back of these doors?
In regards to the gable walls in the 2 dormer rooms there is plaster board stuck onto the outside block. Do we have to do anything to these walls i.e. seal them and replace the plasterboard?
As regards the ceilings in the dormer rooms, would it be necessary to take down the ceiling board and replace with newer insulated board as was suggested to us?
Anyone able to advise?
Thank you.
Thanks for your kind comments
Kind Regards
Shesty and abbey
i normal advise Clients firstly to insulation the ceiling with insulation on top of the slabs.
Next insulate the external walls.
Next fit double glazing with draught proof frames to windows and external doors.
The floor should be the last to be insulated.
The best and most expensive job to do on the timber suspended ground floors is to remove all the timber. Block the vents and fit a DPM/ Radon Barrier, put insulation on top of it and pour a concrete floor on top. I would only recommend this if you have plenty of cash.
Not a lot of heat is lost by Conduction through a ground floor in our mild climate.
thanks C Eastwood for taking the time to give such a detailed reply.
Much appreciated.
Shesty
Insulating the external walls, is a good method of reducing heat loss by Conduction.
Your house was constructed in the 60’s, so it is possible that the external walls are constructed with 225 mm Cavity concrete Blocks, with 2 cavities in each block. This wall is referred to as a Cavity block constructed wall. (Or hollow block Constructed wall)
100 mm block outside with a 50 mm cavity and a 100 mm concrete block/timberframe inside wall is called a Cavity constructed wall.
The external walls of your house may also be s 225 mm solid concrete blocks.
The U value of these walls will be a heat loss of approx 2.1 watts/ m2 / degree C/ hr.
The cavities in Cavity blocks must Never be filled with any insulation.
Both the Cavity Block wall, and solid concrete block walls can be Insulated Externally or Internally.
Internal insulation approx 65 mm + 12 slab fixed internally will meet the Building Regulations (BR) to give a U value of approx 0.35 Watts / m2/degreeC/hour. (On any of the 3 types of walls mentioned above.)
This will reduce your heat loss by conduction to 1/6th.
This will allow you to do 1 room at a time to suit your budget.
It is also recommend fixing a slab with approx 20 mm insulation to internal concrete block partitions which are connected to the external walls- because these will become Cold-bridges when you insulated the external walls internally.
It will also be necessary to fit 10 mm to 20 mm insulation + slab to the 3 reveals of each window. (Assuming a window board).
I will reply re timber suspended ground floors soon.
A
A fair point.We were only discussing this evening, we will internally board some of the walls as we do work on them in the coming months, with insulated board.
We also have suspended floors downstairs which are pretty much just wind tunnels!Not quite sure what is under there yet, but it may warrant filling with some sort of insulation too.We will lift a few boards in the next few weeks and see what is going on.
All of this is very money- dependent here obviously.
shesty
Many people are having external insulation fitted to their homes.
All the Retrofitters will advise them that it’s the best thing to do. And it is the best thing for them to take as much money that they can get from the home owner and do a little work as is possible in a very short time.
Unfortunately when heat loss from the house gets into the cavity, the heat will rise up in the ventilated cavity, and escape through the top of the open cavities.
Meanwhile, the external insulation is waiting outside and wondering - when is the heat going to come out. 😂😂😂😂😂😂😂
Reading with interest as we have a 1960s dormer that eh...evolved... over the years.We moved in late last year and have had a very cold few months.
We are going to go with external insulation most likely.The evolution of the house, and the way it was constructed suggests to us that pumping the walls may not be straight forward and therefore, not worth the attempt.
First off we have put in the correct size boiler, and changed over to natural gas.Significant difference in how quickly the house heats up.Secondly we are in the process of putting a PVC composite front door and a PVc back door.This has made a huge difference in the hall, and take all the drafts out of it.
Neither of us are keen on spray foam, as there is a suspicion it may cause rot on roof timbers over time (we work in construction), but reading the above, I think we will need to consider it for awkward to reach parts of the attic, - and there are a few of those.
We recently bought an insert stove for the fireplace - blocks the chimney but you still have a fire.We had one in a previous house and loved it.
I fully agree on blocking up access hatches to the attic with insulated board or similar behind a door,as this is a very effective way to cut off draughts.
We will eventually do all the windows also.And eventually change to a heat pump, but not until we have done a good bit more on insulating.Among other things.
In no particular order,
The house here is a dormer bungalow, 32 years old, and traditional construction, but the words I've used to describe it is that we had a period of construction in the noughties that were built by Celtic Cowboys, and the builders that built our part of the estate were responsible for training the Celtic Cowboys, and 30+ years ago, the levels of supervision and accountability for complying with the even poorer standards that were in place at that time was effectively zero.
So, this house was COLD, despite having a well specified oil heating system, and after the first winter, I went investigating to try and work out why.
It wasn't hard. The builders has massively skimped on the fibreglass insulation, like putting nothing in to the internal walls on the upper floor, and there was a massive issue with there being no sealing or insulation to prevent the winds that came in from outside from howling straight through under the upstairs floor, and going out the other side and taking a lot of heat with it. 19 Rolls of fibreglass later we had as much as we could of that issue resolved, but there were places where it wasn't possible to get fibreglass in.
The ends of the joists under the internal walls were not closed, and there was no insulation under the upper floor, and to make things worse, all the lights in the downstairs celling were halogen downlighters, and of a design that was very much NOT airtight. The draughts through the downlighters was only massive, so the first job there was to get a large number of catering size (baked bean) tins from a local coffee shop, and fit them over all the accessible downlights to seal the gaps while keeping the insulation away from the lights, the transformers were put on top of the tins to make sure they stayed where they were put, and to keep them out of the fibreglass. The ends of the joist under the internal walls were closed with polystyrene sheeting, and the internal walls were also fibreglassed to improve their insulation. That made a significant difference, but there was still an issue with wind in the crawl spaces that made things difficult, but at least now it was possible to get the house warm when we needed it to be, but it was clear that there were still issues. Oil wasn't a massive price in those times, and there were no easy options to improve things.
Roll on to more recent times. SEAI had a scheme for pumping beads into cavity walls, which we qualified for, and while there was polysytrene sheet in the cavity, the pumped beads made a difference.
In early 2020, all the downlighters were taken out, and replaced by a much better fitting LED light that sealed the gaps, so no more draughts through the ceilings, and a significant decrease in the electricity needed for lighting, there were 9 halogen lights in the kitchen alone, and the LED's reduced the demand there from 450W to 63W, as well as sealing the gaps.
We were looking at maybe a heat pump in 2020, and as a prequalification, we had a BER done, and it came in as a C1, to improve on it was going to need several big ticket projects, so the heat pump went on hold, and we've concentrated on other issues to improve things.
The most recent change has been to get the roof foam sprayed, and that has been a massive improvement, it was evident within hours of doing the job that the winds were for the first time no longer getting into the roof, and taking the heat with them. Effectively, the foam has provided the draught sealing that was needed to retain the heat, and we've very much noticed a massive difference in the temperatures in the upper floor, in both directions, it's cooler in the summer, and was warmer during the winter, most of the time without having to put the radiators on the upper floor on at all, and our oil burn this winter has been significantly lower, partly because it's been a milder winter, but also because there are not the draughts sucking the heat out.
It's also quieter in the upstairs rooms, while that wasn't as such a selling point, being under a Dublin Airport departure and arrival route, the noise reduction has been helpful.
As an experiment, we also changed one window and reglazed the patio door with lower value glass, and that's driven a decision to now replace all the windows later this year with new units, while they were double glazed, the energy loss through them is significant, and we noticed a difference in the 2 rooms that were upgraded, so it wasn't hard to see the potential benefits to be gained from doing all of the windows and doors.
The biggest change from all of the above was to get the roof sprayed, the crawl spaces are relatively small, as is the space above the dormer rooms, but the difference has been massive, and that's down to stopping the free movement of air that came in through the fascias and took the heat with it on the way out of the other side. The crawl spaces don't get that hot as such, as the fibreglass on the ceilings did a reasonable job, but there were too many places where it wasn't possible to get good insulation, and the draughts took full advantage of that. Now, with some careful preparation before the spraying was done, the draughts are gone, completely, so that's made a huge difference. The roof here is large, 20 Mtrs x 7. with an extension on the front, so close on 300 Sq mtrs of tile area, it wasn't possible to spray the whole area in one day, but it wasn't a full 2 days to do it, and the lads that did the job were good, and left the place tidy after they'd finished, so we were very happy with the end result.
Hope that helps some of the people asking, it's taken a long time for appropriate options to become available, and we're not completely there yet, but we're in a much better place costs wise than we were, which is just as well given what's happening at the moment with energy prices.
Once the windows and doors are done, we then are considering removing the one remaining open chimney to reduce the air changes, and I suspect that all of the other changes since the 2020 BER should bring us to a high B rating, and if we were to then add some Solar PV, that might even get us into a low A rating, and help with the ongoing electricity costs.
As for a heat pump, that needs some newer technology for us to go that route, underfloor heating is not an option, I don't want the hassles of tearing out over 200 Sq Metres of tiles, the cost of doing that, and reinstating afterwards with new floor covering is just too much pain, and new radiators throughout would push the costs way up, so that's going to have to wait.
Abbey
I always advise all my clients that they should not use Spray Foam insulation in the Attic
it will not stop all of the heat losses by draughts (Convection)
Reading the above with interest.
We too are interested in improving the comfort level of our 15 year old dormer. It was suggested to us that an alternative to spray foam was Super Quilt.
Has anyone used this to insulate the rafters in their dormer attic spaces? If so, how do they find it? Is it useful in cutting down on draughts?
Brenlizzy wrote: » Anyone make any progress with insulating their dormer? We're in the same boat right now, confused with all the different options.
