Drylining around window reveals?

castleking1

Hi Folks
Building a standard masonery house 100mm cavity, 60mm insulation.
Builder is starting in next few days and need advice on which way to build around window openings as my architect says he should step in a little in the inner leaf to enable 62.5mm dry lining board to fit next to window. Architect hasnt been down this road before and im also unsure. Heard different opinions:
1. Plaster reveals normally (gives better support to window), running drylining flush with reveal.
2. Put narrow strip of plasterboard next to window and skim over.
3. Put insulated dry-lining board in so as the reveals are fully insulated, but builder would need to step his inner leaf in a bit. He is unsure of how to do that.
4. Use a product i received from the local builders provider (roof insulation under plasterboard and skimmed) This roof insulation has 14 layers, very thin.

What to do?
What experiences have you all had?

Poor Uncle Tom

In this detail they haven't stepped back the blockwork, or here either but I would and have asked for the blockwork to be returned sooner at both sides. It becomes a problem at the lintol, however and all I've done here is to return a sheet of plasterboard on its own.

sydthebeat

the step in is a good detail.

Most window manufacturers will measure the opes but leave 10-15mm on all sides for installation. This is a nightmare to make air tight. Expaned foam doesnt cut it!!

It increases the air tightness of the final detail by fitting the window frame tight against the outer leaf with a flexible sealant. Also, the drylining board is held to the window with a steel channel which is also sealed to the window frame.

Id also suggest using the proprietary insulated cavity closers.

The windows obviously have to be installed from the internal.

PaleRider

Castleking,
Take a good look at Sydthebeat pictures xtherm i believe, that detail is very good which shows the inner cavity, and how it insulated. The Library should have the homebond book which has excellent detail on this. There is foil backed insulation strips for doing this detail, they come in lengths 100mm wide. The insulation detail on the inside revels could be done with thin insulation backed plasterboard. I dont believe it is a good idea to move in the inner block, so as to allow for extra insulation. Be careful with the inner wall insulation, depending on the type of board, in any case it should always air tight/sealed/ no air should get behind boards.Thermal bridging Detailing is very important, therefore a good question, hope this is of some help. Regards

castleking1

Yeah I reckon that ill leave openings as standard and maybe get thinner insulated boards, even though they will cover more of window frame.

braftery

Hi there,

You need to take both the internal and external finishes into account when looking at the block details.

The norms for window installation is 10mm-15mm all round. In europe 15mm is mandatory .. this is to ensure that you can get a good fill of expanding foam into the gap to extend the insulation from the cavity to the window. 5mm tolerance will not allow enough room for the foam and it will never fill the gap properly.

It is ideal that both the internal and the external finish cover 5mm to 10mm max of the window frame .

Lastly if you have large glazed units and you are stepping in the inner block layer .. you need to take into account the steel straps that most reputable window installers will use. These should not have too big an angle on them as they are what is holding the unit in place against wind load.

If you contact a window supplier they will probably have details for this or at least be able to give you some advice.

martin46585

you may like to ask your window supplier about a deeper window section, 60mm in fairly standard with pvc, though you can also get a 70mm section, that is more frame between the glass and reveal, the extra 10mm may not seem alot, though it will allow you to return the reveal with a thermal board, all be it a fairly slim one................

saltandpepper10

have worked in a house where the owner thought he was one step ahead of everyone else with his inner leaf of breeze blocks would you believe stepped back to acc 100m insulated board,to cut a long story short what a fcuking mess after windows were fitted we need to chillaxe a little bit on this insulation thing in ireland, were getting obsessed,we should wait till the systems to build fully passive houses become mainstream and affordable imo ireland isnt that cold. normal window fitting techniques will not work in this situation,all these comments are imo by the way

Poor Uncle Tom

saltandpepper10 wrote: »

have worked in a house where the owner thought he was one step ahead of everyone else with his inner leaf of breeze blocks would you believe stepped back to acc 100m insulated board,to cut a long story short what a fcuking mess after windows were fitted we need to chillaxe a little bit on this insulation thing in ireland, were getting obsessed,we should wait till the systems to build fully passive houses become mainstream and affordable imo ireland isnt that cold. normal window fitting techniques will not work in this situation,all these comments are imo by the way

With current Building Regulations on Insulation, Air Tightness and cold bridging as well as trying to obtain a low u value and get a good overall BER rating on a house, not just for resale purposes but to lower the running costs for the homeowner it is not hard to see why people are trying to get a very good standard of finish, and this can only be achieved by paying attention to the small details that make up the overall package.

braftery

Alot of the issues being discussed here are because we are adapting cavity wall construction methods to the requirement for greater insulation.

Throughout alot of Europe the preferred construction method uses external insulation. In pure insulation terms I think this makes sense, as you are keeping the concrete block warm and it acts like a capacitor to store the heat for your home inside the insulation. Cavity wall construction is primarily designed to ensure moisture is kept out the outer course and not allowed to pass to the inside course and get into the house.

To my mind, insulating using warm board on the insdie of the block, will mean that the block will be cooler and will draw heat from the building faster.

If anyone can give me more information about this i would be grateful.