Insulation specification thoughts

Rooy

Hi , have been a keen reader on here for past few months , recently got planning for 1.5 storey 289sq meter house and am now working together with architect on builders specification to go to tender with.
I guess in general I am looking for a fairly decent level of air tightness and insulation .I will be using oil heating.
I know there can a lot of different opinions on insulation ,so I was hoping for some short feedback on whether any concerns with the following my architect has drawn up :

Floor :
Concrete ground floor slab throughout shall be 150mm thick 30 N. concrete slab with a power floated finish, on 120 mm XtraTherm floor slab insulation board .

External Walls :
100mm Outer leaf , 100mm inner leaf ,. 100mm wide cavity insulated using 100mm XtraTherm cavity therm. drylined internally using 62mm thick insulated plaster boards

First floor Ceiling :
Line all internal partitions and ground floor ceilings with 12.7 gyproc plasterboard.
Supply and lay 300mm thick fibreglass insulation quilt to all attic spaces with flat ceilings . All sloping areas and the flat roofed rear annex shall be insulated with 100mm XtraTherm or similar approved

Roof :
Fitted between the rafters and ceilings underneath shall be drylined using 63mm thick insulated plasterboard , incorporating a vapour check.
*We are laying chipboard floor in attic for storage , maybe that is why specification also includes roof insulation, I need to confirm this.

BryanF

air-tightness?

Rooy

Thanks for the response Bryan , in terms of the draft specification it specifies ". Allow for the insulation of an air tightness membrane and for testing and certifying same" .
I have been reading through it over the weekend before meeting the architect again ,but this sounds possibly like it needs more detail added.

sydthebeat

firstly, internal dry lining on a new house build is a bad specification.

secondly, most of the specification is just barely on the minimum level required.

has a provision BER assessment been carried out to show the whole house specification complies?

if so, what level of air tightness was inputted and how was this measure treated in the specification?

Strolling Bones

Rooy wrote: »

Thanks for the response Bryan , in terms of the draft specification it specifies ". Allow for the insulation of an air tightness membrane and for testing and certifying same" .
I have been reading through it over the weekend before meeting the architect again ,but this sounds possibly like it needs more detail added.

That sounds like it was written by a badly performing student. How did you find this "architect"?

sky6

Some of these methods sound out of date by modern standards. With the amount of money you'll be spending you need to get it right. Don't rush to build, Do plenty of research and talk to lots of people. Don't be afraid to contact the manufacturers to find out how they recommend it's fitted or done. Don't take or give any instructions verbally.
Remember if your getting a Mortgage you will be paying it for a long time.

Rooy

Thanks for the feedback guys , I guess it highlighted my shortcomings in an understanding of all this , great to get some comments , I can going to look to get an independent BER assessment on the initial specification and see what I can consider to change from there as well as seek further advice where possible.

sydthebeat

Rooy wrote: »

Thanks for the feedback guys , I guess it highlighted my shortcomings in an understanding of all this , great to get some comments , I can going to look to get an independent BER assessment on the initial specification and see what I can consider to change from there as well as seek further advice where possible.

make sure the assessor is a qualified architectural technician

BarryM3

sydthebeat wrote: »

firstly, internal dry lining on a new house build is a bad specification.

Can you elaborate on this please, it has been spec'd into my own build by my BER assessor.

Are you saying that installing the insulated board is not only bad but also unnecessary and if so should I be replacing it with another type of insulation?

My spec is a 150mm bead cavity with sand/cement plaster and 50mm insulated board on all external walls.

Minimum of 2 required on air tightness (hoping for better than that) and installing a MHRV system.

sydthebeat

BarryM3 wrote: »

Can you elaborate on this please, it has been spec'd into my own build by my BER assessor.

Are you saying that installing the insulated board is not only bad but also unnecessary and if so should I be replacing it with another type of insulation?

My spec is a 150mm bead cavity with sand/cement plaster and 50mm insulated board on all external walls.

Minimum of 2 required on air tightness (hoping for better than that) and installing a MHRV system.

The current building regulations are of a quite high standard.
They are designed in essence to avoid the "warm up - cool down" frequencies that we were all brought up with in irish homes, where we get out of bed to a freezing cold house. Now we try to maintain a constant comfortable temperature using the least amount of fuel as possible.

One factor which helps in regulating temperature so not to have highs and lows is "thermal mass". This means dense materials such as concrete absorb the heat during the day, whether by solar gain, or by generated energy, and store this heat and releases it back at night time when temps drop and theres a bigger demand.

Another factor which helps regulate this air tightness, which basically means cutting out any unwanted draughts. In order to achieve as high a possible an air tightness, the construction should be kept as homogeneous as possible and the details as simple as possible.

by specifying thermal liners on the external walls, the thermal mas is reduced significantly. While its arguable that this deflects the heat generated quicker than block walls, it also means that the rooms cool down quicker also. This results in a pattern of heating up / cooling down that we are trying to avoid. It also means that more heat needs to be generated at times when temps are lower such as evening and night time.

when it comes to air tightness, thermal liners are a bad idea. It becomes extremely hard to guarantee good detail because less care is taken with things such as the initial block work, chasing etc as "sure it will be covered over" mindset kicks in. Imagine how difficult it is in making a timber joist floor air tight if the air tight layer is 50mm inside the external walls.

also, you end up having a break in your insulation continuity at ever location of an internal wall meeting an external, and at first floor junctions. Whilst you still have the cavity insulation, your extra insulation is broken at all these points and these areas run the risk of condensation being localized and intensified, whcih can cause additional issues.

the solution is either to
1. increase the cavity width to account for the internal insulation, say to 200mm (this may need your structural enginners input)
2. install a cavity board insulation such as xtratherms full fill cavity board in your 150mm cavity.

in my opinion both the options above are better solutions than using internal dry lining.

its much easier to treat internal blockwork for air tightness, than dry lining.

BarryM3

Thanks for that Syd.

If you were in my shoes, i.e committed to 150mm cavity what would you do?

Edit to add: I understand the thermal mass concept and it's benefits and downsides. We have chosen not to go this route due to our lifestyles and daily habits.

If someone could show me that I would be no worse off by ditching the insulated board I would be quite happy to delete it off my spec and spend the money elsewhere.

sydthebeat

BarryM3 wrote: »

Thanks for that Syd.

If you were in my shoes, i.e committed to 150mm cavity what would you do?

committed as in the blockwork is significantly up already?

BarryM3

Foundations, rising walls and floor filled in with stone

sydthebeat

BarryM3 wrote: »

Foundations, rising walls and floor filled in with stone

id change my cavity specification to full fill insulation such as ive linked to above.

have you anyone working on the construction details of your build, especially from an air tightness point of view?

BarryM3

And would you delete the application of insulated board then?

Yes, I've a BER assessor who is working with my structural engineer/Architect in creating necessary detailing and liaising with the contractor in all areas including air-tightness, cold bridging etc. I need to check but I think the contractor is in turn out-sourcing the air-tightness procedures.

In relation to the full fill Vs cavity bead I did some research a while back on both and came to the (possibly wrong?) conclusion that while the cavity board can give better U value results it is very much dependent on an almost flawless installation which is extremely difficult and realistically unlikely to achieve. I remember something about it losing a significant % of it's performance if a gap of something like 2mm at any point?

sydthebeat

BarryM3 wrote: »

And would you delete the application of insulated board then?

Yes, I've a BER assessor who is working with my structural engineer/Architect in creating necessary detailing and liaising with the contractor in all areas including air-tightness, cold bridging etc. I need to check but I think the contractor is in turn out-sourcing the air-tightness procedures.

In relation to the full fill Vs cavity bead I did some research a while back on both and came to the (possibly wrong?) conclusion that while the cavity board can give better U value results it is very much dependent on an almost flawless installation which is extremely difficult and realistically unlikely to achieve. I remember something about it losing a significant % of it's performance if a gap of something like 2mm at any point?

that is true and i would have held a similar opinion up to having reviewed a few projects using the product lately, and, ONCE DUE CARE is applied and the product is installed correctly in accordance with datasheets, then id have no problem recommending it. It was outr standard spec up to last year to pump the cavities and, while i still believe in it as a specification, ive seen cases where DPC trays are put in taut which means the beads cant fill the areas behind. Again its a case of block layers not caring understanding whats coming after them....

so in your particular case, if you haunt your blocklayer and make sure the cavities are clean and the insulation is installed correctly, id still prefer this to using thermal lining boards.
on a risk versus reward basis id view the dry lining as a higher risk for less reward.

BarryM3

Thanks Syd,

I will speak to the contractor and his blocklayers and suss out the option of using the board and their personal experiences.

One final aspect.... supposing, for whatever reason, we retain the bead filled cavity option....would you keep the insulated boards or bin em?

galwaytt

sydthebeat wrote: »

The current building regulations are of a quite high standard.
They are designed in essence to avoid the "warm up - cool down" frequencies that we were all brought up with in irish homes, where we get out of bed to a freezing cold house. Now we try to maintain a constant comfortable temperature using the least amount of fuel as possible.

One factor which helps in regulating temperature so not to have highs and lows is "thermal mass". This means dense materials such as concrete absorb the heat during the day, whether by solar gain, or by generated energy, and store this heat and releases it back at night time when temps drop and theres a bigger demand.

Another factor which helps regulate this air tightness, which basically means cutting out any unwanted draughts. In order to achieve as high a possible an air tightness, the construction should be kept as homogeneous as possible and the details as simple as possible.

by specifying thermal liners on the external walls, the thermal mas is reduced significantly. While its arguable that this deflects the heat generated quicker than block walls, it also means that the rooms cool down quicker also. This results in a pattern of heating up / cooling down that we are trying to avoid. It also means that more heat needs to be generated at times when temps are lower such as evening and night time.

when it comes to air tightness, thermal liners are a bad idea. It becomes extremely hard to guarantee good detail because less care is taken with things such as the initial block work, chasing etc as "sure it will be covered over" mindset kicks in. Imagine how difficult it is in making a timber joist floor air tight if the air tight layer is 50mm inside the external walls.

also, you end up having a break in your insulation continuity at ever location of an internal wall meeting an external, and at first floor junctions. Whilst you still have the cavity insulation, your extra insulation is broken at all these points and these areas run the risk of condensation being localized and intensified, whcih can cause additional issues.

the solution is either to
1. increase the cavity width to account for the internal insulation, say to 200mm (this may need your structural enginners input)
2. install a cavity board insulation such as xtratherms full fill cavity board in your 150mm cavity.

in my opinion both the options above are better solutions than using internal dry lining.

its much easier to treat internal blockwork for air tightness, than dry lining.

I won't point you in the direction of a scheme of 60+ houses being built now with 100mm insulated board on the inside so !!

sydthebeat

galwaytt wrote: »

I won't point you in the direction of a scheme of 60+ houses being built now with 100mm insulated board on the inside so !!

a block build?

wouldnt at all surprise me that a developer will choose the quickest, driest method which ticks the paper exercise of Part L compliance.

ferryman35

We are putting the finishing touches to the outside of our build and I would recommend the full fill board as recommended here hands down.

Because you are filling the cavity it is not so difficult to get a tight fit of the insulation to the inner leaf. The edges of the boards are rebated and 'slot' into each other, so you've actually to work to get an open gap. The corner boards come pre-mitred so jointing there isn't so difficult either. If you wanted a really good result you could tape the joints in the boards and it might especially be worth doing at the corners.

The only downside of this product is that there can be a bit of waste an the sloped parts of the gable walls. (And the blocklayers won't want anything that slows them down!)

You'll find many benefits as you progress into your build with having masonry rather than plasterboard walls to work with

You're also at the stage that it would be prudent to consider using quinnlites for your first and last courses on the internal leaf and you'll find more threads about that measure in the forum. Though I tried I wasn't as successful as I hoped to be getting my guys to do this, but I got them some places!!

And another good tip that you'll find here is to locate your meter cabinet on a garage wall rather than the house wall if you are building a suitably located garage.

The recommendations you've been given here are spot on, and much more progressive than many of the specifications that seem to be going into even pretty expensive builds at the moment.

We finished ours off with a rockwool based warm roof construction and the builders are amazed at the heat they can feel when they step inside - and its just a shell!! It's not just placebo....you'd take your jacket off to walk around inside.

BarryM3

So, here is the ultimate question.

150mm full full cavity and no insulated board
or
150mm bead fill cavity and insulated board

Which is better overall? Anecdotally and U value wise?

It just seems to me that ditching the insulated board will reduce the insulation quality of the house more than the full fill board can make up?

Ferryman - In relation to QuinnLites, I have that spec'd into the plans.

Is having plasterboard covered masonry walls really that big a deal, surely you can just drill deeper holes and affix to the masonry behind the board where required?

beyondpassive

Drylines eliminates mass from the building and affects the aility of the interior to maintain stable heat and deal with overheating. Drylining is also a fire risk but less about that. One issue is that the dryling stops and starts at partitions, suspended floors and eaves. When i look at my own refurb with its drylining, you can see heat escaping at the 1st floor floorplate, where the heating pipes occur.

In my view your better with a lesser U-Value and higher mass. Personally i think drylining should be allowed for new build.

ferryman35

the quoted u-value for 150mm full fill well meets the regulations, so if you have a good installation, then you should expect a good result. Anecdotally is harder to quantify.

At the end of your project, all the components of your build have to function as a system, and it is how you combine the different elements that will determine your success. Insulation is only part of the equation - you also need to keep airtightness, ventilation and the heating system in mind.

The best demonstration I saw of thermal mass in action was after the sun had set during the summer evenings....you could feel the heat radiating back from the blocks in the cooler night air. It works....

In a new house that I saw, with insulated board on the internal walls and hole in the window vents, the tiniest fire had heated the sitting room so hot and stuffy that we couldn't stay in it. Yet a part of the house that didn't have heating on was freezing - too cold to stand in without your jacket.

You won't reduce the insulation value of your house but you will make it a whole lot more comfortable......and you don't have he risk of condensation & mould.

And your second question.....yes you can drill deeper holes and fix to the masonry behind, but then if you're fixing something heavy you should be using spacer blocks (don't see those in too many places!?.....you need special fixings for lights, pictures, hanging shelves, more complicated for airtightness, probably wiring if its done right and fitted furniture.

There are places where insulated boards are a very good solution but I think there are better options for new builds.

antiskeptic

BarryM3 wrote: »

So, here is the ultimate question.

150mm full full cavity and no insulated board
or
150mm bead fill cavity and insulated board

Which is better overall? Anecdotally and U value wise?

It just seems to me that ditching the insulated board will reduce the insulation quality of the house more than the full fill board can make up?

Ferryman - In relation to QuinnLites, I have that spec'd into the plans.

Is having plasterboard covered masonry walls really that big a deal, surely you can just drill deeper holes and affix to the masonry behind the board where required?

What about downstairs internal walls (or some of them) of blockwork to give you thermal mass and insulate the external walls internally as planned. We went lightweight block on the insulated slab in places - more for sense of solidity.

What of your floors? Are they concrete and would that not contribute to thermal mass?

-

For what it's worth. I've had experience of renovating/living in two identical houses, one with 60mm insulation in the cavity and one with 60mm insulated slab on all external walls. I get the thermal mass argument but:

- the internal slab version seems more forgiving of builder sloppiness. I couldn't believe what I saw bricklayers doing and went through 4 of them on one build, firing 3 for unforgiveable workmanship.

- the idea of 4'x2'vpieces of insulation, successfully T&G knitted with it's neighbour bottom/top/right/left then clamped tight to a wall strikes me as the height of wishful thinking on site. Perhaps the methods proposed here differ from that. 8x4 gives less margin for error internally.

- I don't see the advantage of "slowly releasing the heat back into the room" when I'm in bed. Zero thermal mass (were such a thing possible) means rapid heat up times which are easy/cheapest of all to sustain for the time you need them and which don't waste heat being given back when you're not around to enjoy it.


Without question and based on comparative experience, especially given the realities of building on site, I'd plump to live in a polyisocyanurate box every time. Remember, thermal mass leaks heat to ground: you get up in the morning to a non ice-box house (yeay!), head out to IKEA for the afternoon, come home, hit the heating ... and wait. Match of the Day is winding up before you're up to speed.

In an ideal world perhaps.

sydthebeat

antiskeptic wrote: »

Remember, thermal mass leaks heat to ground: you get up in the morning to a non ice-box house (yeay!), head out to IKEA for the afternoon, come home, hit the heating ... and wait. Match of the Day is winding up before you're up to speed.

In an ideal world perhaps.

you see this is where you are wrong, with a high thermal mass home if your gone for the afternoon and the heating is off, the thermal mass help regulate the heating so thats theres NOT a sudden drop in temperature while youre out.

they are designed to regulate over 24 hours, not 4 or 5.

the only time id recommend a low thermal mass house is when there is definitely no body in house at all for 8 - 10 hours a day every day....

so for the likes of offices etc it may be a reasonable spec.

antiskeptic

sydthebeat wrote: »

the only time id recommend a low thermal mass house is when there is definitely no body in house at all for 8 - 10 hours a day every day....[/quote

Like (effectively) night time? Every night time I'm snug under the blankets and need no heat being released into the house. Yet lots of the heat I've on to keep me snug for Grand Designs is being absorbed by the walls to be given back out when I'm asleep.

The trouble (I find) with thermal mass is that it's too slow to react to changing requirements: some days folk are out lots of the day, sometimes not. Sometimes you stay in on a Saturday, sometimes you're out for the day. With thermal mass, you're kind of committed to maintaining even temperature 24/7. Without it, you can zap on the heat when you need to zap it on, and get a return quickly.

It's not like you can have no thermal mass such as the house turns to an ice box as soon as you open the front door to take in your Bombay Pantry delivery...

BarryM3

beyondpassive wrote: »

Drylines eliminates mass from the building and affects the aility of the interior to maintain stable heat and deal with overheating. Drylining is also a fire risk but less about that. One issue is that the dryling stops and starts at partitions, suspended floors and eaves. When i look at my own refurb with its drylining, you can see heat escaping at the 1st floor floorplate, where the heating pipes occur.

In my view your better with a lesser U-Value and higher mass. Personally i think drylining should be allowed for new build.

I get the thermal mass point, in my circumstances it's not crucial as our lifestyle dictates large periods of empty house.

In relation to the stop/start of the drylining - I must be missing something. As we will have all external walls wet plastered internally also, then the adding of the insulated drylining - even if done badly - is a positive surely? OK, onthe internal walls (without wet plaster) there could be some escape but that is within the thermal envelope of the house so no big deal?

ferryman35 wrote: »

the quoted u-value for 150mm full fill well meets the regulations, so if you have a good installation, then you should expect a good result. Anecdotally is harder to quantify.

Yes, that will meet regulations but will adding the insulated board not improve the U value. As is always said, the regs are a minimum rather than an absolute target.

ferryman35 wrote: »

In a new house that I saw, with insulated board on the internal walls and hole in the window vents, the tiniest fire had heated the sitting room so hot and stuffy that we couldn't stay in it. Yet a part of the house that didn't have heating on was freezing - too cold to stand in without your jacket.

The MHRV should go some way to ensuring the even distribution of the heat. For example we are speccing a vent to be placed in close proximity to the stoves

ferryman35 wrote: »

You won't reduce the insulation value of your house but you will make it a whole lot more comfortable......and you don't have he risk of condensation & mould.

Surely by removing any form of insulation you are reducing the insulation value of your house? I'm sure there's a 'law of diminishing returns' argument but that aside deleting any insulation will reduce the absolute number?

ferryman35 wrote: »

There are places where insulated boards are a very good solution but I think there are better options for new builds.

For clarity, are you saying that taking into account my particular build/spec that I am better off in everyway without the insulated boards... Trust me, I would love that to be right as I could save a nice few quid - but I ain't convinced....yet!

antiskeptic wrote: »

What about downstairs internal walls (or some of them) of blockwork to give you thermal mass and insulate the external walls internally as planned. We went lightweight block on the insulated slab in places - more for sense of solidity.

What of your floors? Are they concrete and would that not contribute to thermal mass?

All my walls (on both floors) are blockwork and the floors are concrete too.

antiskeptic

BarryM3 wrote: »

All my walls (on both floors) are blockwork and the floors are concrete too.

Would those who champion thermal flywheels consider there to come a point where you simply have too much of it? And therefore consideration need be given to internal surface insulation simply in order to reduce the amount of it? (I have visions of it taking weeks to get the thermal flywheel up to speed - just before you head off to some winter sun :pac:)

Irrespective of detailing, isn't there going to be loss to foundations via internal block walls (and in the case of upstairs floors also concrete, losses to external walls). Even (time)distribution of heat vs. increased heat loss need also be a consideration.

sydthebeat

I give up trying to explain the principles here.... you can lead a house to water. ...

BarryM3

I understand the principles Syd, ultimately the question I am asking - and no one has really answered yet is this:

Putting thermal mass argument aside for a moment (as it doesn't suit my lifestyle)-are you saying I would be better off without insulated boards than with them?

I totally accept the thermal mass principle. My current rent a house has crappy insulation and the coldness coming off the walls is really noticeable.

There seems to be an undertone here that if you don't agree with it you don't understand it - which I think is unfair at best...

Being vague and flippant is not big and it's not clever either!

BarryM3

antiskeptic wrote: »

Would those who champion thermal flywheels consider there to come a point where you simply have too much of it? And therefore consideration need be given to internal surface insulation simply in order to reduce the amount of it? (I have visions of it taking weeks to get the thermal flywheel up to speed - just before you head off to some winter sun :pac:)

Irrespective of detailing, isn't there going to be loss to foundations via internal block walls (and in the case of upstairs floors also concrete, losses to external walls). Even (time)distribution of heat vs. increased heat loss need also be a consideration.

There is specific detailing to stop cold bridging at the points you mentioned.