insulated plasterboard

atlonglast

Our house has been built with a 150mm cavity which we are going to fill with beads. Could anyone tell me what the difference in u value would be if we put 50mm plasterboard on the walls also?

BryanF

atlonglast wrote: »

Our house has been built with a 150mm cavity which we are going to fill with beads. Could anyone tell me what the difference in u value would be if we put 50mm plasterboard on the walls also?

1. what is the w/mk of the beads under normal conditions (not in the lab)?
2. what did your BER assessor have to say?
3. and what did your architect advise?
4. why did your design team, not know this before you started on site?

muffler

BryanF wrote: »

1. what is the w/mk of the beads under normal conditions (not in the lab)?
2. what did your BER assessor have to say?
3. and what did your architect advise?
4. why did your design team, not know this before you started on site?

Listen, its a simple question and I dont think the OP came here to get the 3rd degree.

Just pass if you dont feel like answering. Thanks

sydthebeat

150 pumped = 0.2

With insulated board = 0.17

'ish'

tred

muffler wrote: »

Listen, its a simple question and I dont think the OP came here to get the 3rd degree.

Just pass if you dont feel like answering. Thanks

I think BryanF must have a macro written to auto reply certain posts

BryanF

apologies mods for taking the thread of topic, but it think the OP got his/her question answered.

tred wrote: »

I think BryanF must have a macro written to auto reply certain posts

. yes it must seem like that all right. its simply frustrating to see people make the same mistakes again and again. this week alone if you look around boards.ie you can see several people who have posted regularly since the start of their extension/new home project, all the time being advised to get certain construction issues covered before starting on-site.

There is an old but very wise adage used in carpentry “Measure twice, cut once” which is typically followed by “you can’t add wood back”. The message is simple: proper planning will eliminate mistakes.

I shouldnt complain though - a fare % of my work is on-site problem solving issues that would easily have been avoided, if they was a proper spec and set of drawings prepared at tender stage.:D

as pointed out by syd and Muffler, everyone has the right to ask whatever question they want and receive a civil answer, and pushing professional involvement should be left for those that ask/need that advice - I'll hold my hand up and say I sometimes over step that mark, but on the other hand, the phrase 'i told you so' might slip out if i didnt have a few 'auto replys'.. (not that it ever would:D)

beyondpassive

atlonglast wrote: »

Our house has been built with a 150mm cavity which we are going to fill with beads. Could anyone tell me what the difference in u value would be if we put 50mm plasterboard on the walls also?

Another stock question and so a stock answer.

Insulating the inside of the walls might improve the walls U-value but will eliminate the thermal capacity benefit of having masonery walls. You will therefore not really get any benefit from charging the underfloor from your thermal store in spring and Autumn. Also the dryling is compromised at cross walls, floors and junction boxes and even at the joints between panels. In short its dumb. At this late stage, compensate by overinsulating the roof and go for treble glazing and MHRV.

sinnerboy

+1 upgrade your windows not the external walls . Or air tightness. Or ventilation strategy. Or hire a good BER Assessor to go through all of the above.

bbam

atlonglast wrote: »

Our house has been built with a 150mm cavity which we are going to fill with beads. Could anyone tell me what the difference in u value would be if we put 50mm plasterboard on the walls also?

We built with 100mm cavity and 50mm high density insulated slabs on the inside and we are very happy, it's a number of years ago now and nothing but positives. Only regret was we didnt go for a larger cavity like yourself.

Fracking Cylon

bbam wrote: »

We built with 100mm cavity and 50mm high density insulated slabs on the inside and we are very happy, it's a number of years ago now and nothing but positives. Only regret was we didnt go for a larger cavity like yourself.

I think the trade off is if you had your time back, and went for the 150 mm cavity, would you still have gone for the insulated board? I would think 150mm pumped cavity is enough, and not worth the expense of adding the 50mm insulated slab.

BryanF

Fracking Cylon wrote: »

I think the trade off is if you had your time back, and went for the 150 mm cavity, would you still have gone for the insulated board? I would think 150mm pumped cavity is enough, and not worth the expense of adding the 50mm insulated slab.

comply with current regs with a 150 cav pumped?

bbam

Fracking Cylon wrote: »

I think the trade off is if you had your time back, and went for the 150 mm cavity, would you still have gone for the insulated board? I would think 150mm pumped cavity is enough, and not worth the expense of adding the 50mm insulated slab.

Yes I would still have done both...

sydthebeat

BryanF wrote: »

comply with current regs with a 150 cav pumped?

quite possibly....

interestingly i did a cost benefit analysis on upgrading a 150 pumped cavity (0.2 u value) and an upgrade of 32.5 insulated plasterboard (0.17 u value) on a house with wood pellet fuel..... using DEAP as the primary tool.

the savings on this were €549 over 20 years and €2,815 over 50 years.

even at 2008 reg levels, this kind of upgrade makes very little difference from an energy value point of view. In this instance it was a difference of 1.38 kwhr/m2/yr or 369.5 kwhrs/yr.

0.0499 per kwhr @ approx 4% increase annually.


makes a lot more sense if you are using oil as your main fuel
0.1254 per kwhr @ approx 8-9% increase annually.

the keen edge

I'm more or less at the same stage in a self build as the OP.

External work is completely finished(windows fitted, external rendering finished and painted, landscaping completed), however the internal work is only starting now. (The build is a long term project and I didn't want the place looking like a building site for a number of years!, hence the works have been scheduled in this manner.)

I have a 150mm cavity(will be pumped), roof space will be fully insulated as required and a HRV system will be installed.

The engineer signing off on the build is also a BER assessor.
He has advised fitting insulated plasterboard slabs to the external walls, and without giving it much thought myself I had planned on doing so.

However is the general consensus here against such an approach?.

about2build

Like the keen edge i'm in a similar position and will be 150mm pumped cavity and am having a 67.5mm insulation board installed on the external walls which should give a u-value of .13. Having read this thread it now seems like excessive though i am going for high levels of insulation throughout incle treble glazed and mhrv...

BryanF

the keen edge wrote: »

However is the general consensus here against such an approach?.

the question I would ask is why build a cavity and then dry line? why not build a cavity wide enough to accommodate the insulation/U-value required?

about2build wrote: »

i'm in a similar position and will be 150mm pumped cavity and am having a 67.5mm insulation board installed on the external walls which should give a u-value of .13. Having read this thread it now seems like excessive though i am going

the U-value you state is imo NOT excessive but does of course depend how compact the plan/ext surface is. 150mm cavity with pumped bead is not adequate, if it was why had you and the other posters planned to dry line? - A 300mm cavity will bring you to approx 0.1W/m2K, so somewhere in the middle should be fine for a compact house.
the point I see made in this thread is - if you have NOT done your homework and once on-site dry-lining is been suggested as well as a 150mm cavity block wall, MAYBE you should look to achieve building regulation compliance by improving U-values/air-tightness/reduced heating loads elsewhere in the build, instead of adding the dry-lining.
syd's post while interesting, is not referring to a new build wall that has planned, designed and built wide cavity
so for continuity:)
this is the importance of designing and detailing at an early stage so as to avoid these type of on-site debates... the very best of luck with your projects

about2build

Thanks Bryan...i dont know where else i can improve....while still remaining financially cognisant 500mm of wool in roof on the flat, 150mm in floor, triple glazed windows boasting a certification of 0.7 and an air tightness aim of <2 at q 50....the wall is the only real way to improve further

the keen edge

BryanF wrote: »

the question I would ask is why build a cavity and then dry line? why not build a cavity wide enough to accommodate the insulation/U-value required?


the U-value you state is imo NOT excessive but does of course depend how compact the plan/ext surface is. 150mm cavity with pumped bead is not adequate, if it was why had you and the other posters planned to dry line? - A 300mm cavity will bring you to approx 0.1W/m2K, so somewhere in the middle should be fine for a compact house.
the point I see made in this thread is - if you have NOT done your homework and once on-site dry-lining is been suggested as well as a 150mm cavity block wall, MAYBE you should look to achieve building regulation compliance by improving U-values/air-tightness/reduced heating loads elsewhere in the build, instead of adding the dry-lining.
syd's post while interesting, is not referring to a new build wall that has planned, designed and built wide cavity
so for continuity:)
this is the importance of designing and detailing at an early stage so as to avoid these type of on-site debates... the very best of luck with your projects

Thanks for the response, maybe I should have made clear my build specifications.

My externals walls are comprised of concrete blocks (both inner and outer leaf). Are you suggesting that this method of construction can incorporate a >250mm cavity?
Personally I've never seen a (blockwork/brickwork)cavity in excess of 175mm.

Drylining wasn't a late decision made onsite; it was(rightly or wrongly)provisionally planned pre-build.

BryanF

the keen edge wrote: »

Are you suggesting that this method of construction can incorporate a >250mm cavity?

yes - to comply with current regs 200-250 may be adequate depending on building shape/surface area ratio to get you below a U-value of .15w2mk- presuming 0.33wm/k bead - there's lots of similar threads on this topic
http://www.boards.ie/vbulletin/showthread.php?t=2056447289

cavanmann

about2build wrote: »

Like the keen edge i'm in a similar position and will be 150mm pumped cavity and am having a 67.5mm insulation board installed on the external walls which should give a u-value of .13. Having read this thread it now seems like excessive though i am going for high levels of insulation throughout incle treble glazed and mhrv...

I doing the same as you , even thinking of 80mm insulated plaster board which is the 92.5mm over all I dont believe tomuch is excessive see the differsant today of buildings regs compared to last year
It will double in 10 years

Raized

I'm sorry for the thread jack but I'm looking for advice. I had a house build last year and 50mm insulated slab was mounted on the walls that are backing onto external walls. The cavity is 100mm beaded fill. I appear to have round shaped black marks where the mounting srews were inserted on all these wall now. The builder has been informed and is coming to take a look but a heads up on what this is would be a great help:(

the keen edge

Just sounds like a poor plastering job.

Not necessarily particular to your problem, however:
After installing insulated boards, any wall longer than the width of a board(i.e. 4') should be, prior to skimming, straighten out with an undercoat of bonding.

By in large, a skim coat applied straight on to a wall of insulated boards, rudimentary fixed onto blockwork, is never going to be right and true regardless of how good a plaster is with a trowel.

Raized

Thanks for the quick response. So what does the builder have to do to fix it? I am worried that maybe the wrong fixing screws were used and that its cold transfer. Which also makes me ask was the bead filled enough in the cavity. there should be no damp throught the inside leaf surely?

MicktheMan

Raized wrote: »

I'm sorry for the thread jack but I'm looking for advice. I had a house build last year and 50mm insulated slab was mounted on the walls that are backing onto external walls. The cavity is 100mm beaded fill. I appear to have round shaped black marks where the mounting srews were inserted on all these wall now. The builder has been informed and is coming to take a look but a heads up on what this is would be a great help:(

This is caused by high humidity levels in the house.
The mechanical fixing are acting as thermal bridges resulting in very localised cold surfaces below the dew point of the air resulting in mould.
You need to tackle your heating & ventilation regime to solve this.

the keen edge

Apologies, I actually read you post incorrectly, I for some reason read black marks as hollow marks.:o

Raized

the keen edge wrote: »

Apologies, I actually read you post incorrectly, I for some reason read black marks as hollow marks.:o

That's grand:)Thanks for the advice tho, I'm wondering if I chop up the builder and bury his body in the wall cavity would it help...I'd feel better anyway:)

Raized

MicktheMan wrote: »

This is caused by high humidity levels in the house.
The mechanical fixing are acting as thermal bridges resulting in very localised cold surfaces below the dew point of the air resulting in mould.
You need to tackle your heating & ventilation regime to solve this.

Thanks Mick, that makes sense:) But is is the fault of the fixings or the insulation? The house is never damp because I have gas heating and a stove going every night. Where was the error made in the build?

MicktheMan

Raized wrote: »

Thanks Mick, that makes sense:)
1.But is is the fault of the fixings or the insulation?
2.Where was the error made in the build?

1. Neither. This is a "feature" of insulated slab internal dry lining. It is an indication that there may be insufficient ventilation, inadequate heating or elevated internal moisture load allowing the moisture in the air to condense on these localised cold surfaces which mould needs to thrive.
2. At specification stage - not looking at the build as a whole or in a holistic manner.

Raized

MicktheMan wrote: »

1. Neither. This is a "feature" of insulated slab internal dry lining. It is an indication that there may be insufficient ventilation, inadequate heating or elevated internal moisture load allowing the moisture in the air to condense on these localised cold surfaces which mould needs to thrive.
2. At specification stage - not looking at the build as a whole or in a holistic manner.

So I could just paint over it and hope it doesnt appear again? And open the windows more to allow the air circulate in the house? The heating is brilliant in the house so i couldnt see that being and issue but I guess if the moisture is in the air it has to go somehwere. Maybe I should open the vents in the windows too:rolleyes:

Andrew_Doran

Do you get condensation on your windows? What kind of vents do you have in the rooms? Do you block your vents?

If you want to verify that your indoor humidity is good then a tenner will see you a humidity/temperature monitor from eBay (search "temperature humidity"). Ideally you want to be aiming for 60% relative humidity or less.

beyondpassive wrote: »

dryling is compromised at cross walls, floors and junction boxes and even at the joints between panels. In short its dumb.

I wouldn't consider it for a new build but as for retrofitting most of the problems you mention are down to bad design / workmanship, and to the practice of using "warmboards" with combined insulation + plasterboard as opposed to separate layers. I think it can be done reasonably well but at what cost is the question in my mind.

Raized

MicktheMan wrote: »

1. Neither. This is a "feature" of insulated slab internal dry lining. It is an indication that there may be insufficient ventilation, inadequate heating or elevated internal moisture load allowing the moisture in the air to condense on these localised cold surfaces which mould needs to thrive.
2. At specification stage - not looking at the build as a whole or in a holistic manner.

Thanks Mick, so is there anything that can be done to correct this? The mushrooms are showing at lower levels on the walls too so not sure whether to just repaint or not?

topcatcbr

What is the advantage of having a huge cavity.

I think we need to completely rethink how we construct our homes and not just try to make the way we learned how to build to fit the new regulations. In my mind they are not compatible. The only reason for the cavity was to protect from moisture ingress. This can be done other ways. Rain screen cladding with external insulation board for example.

I designed a few homes not too long ago that are near passive. They were all built block on flat with all insulation on the outside and had conc first floor. This gives maximum thermal mass/balance with any solar gain being absorbed during the day. It's is also a very cost effective method of construction.

Very important to all this is aspect air tightness and HRV.

Seany1981

Externally insulated blockwork cost effective?? How have you determined this? I can't seem to get external insulation and render for less than €80/m2. This excludes to blockwork. This is very expensive in comparison to pumped cavity or partial fill cavity.

tred

I think a key piece of the jigsaw here also is your heating source. If you are using a geo system with underfloor where you are trying to maintain a constant temp in the house 24X7, then you have to think about thermal gain here, which was eluded to by Beyondpassive earlier in this thread, let the block work retain some of the heat. I think if you are using more conventional heating system, such as radiators, the drylining might make more sense. shorter bursts of heat that you are trying to retain inside the envelope longer. People sometimes assume today all new builds are underfloor. Some people dont like the sweaty feet syndrome and are going for Radiators (alu even)..that business is not declining as much as one might believe.

SpudBr

The house I have is made from solid walls , built about 1850 . I want to put insulated plasterboard on two external walls of one of the rooms only . Will that cause a "cold bridge effect " on firstly the mushrooms which connect the plasterboard to the wall and secondly around the edges of the plasterboard?