250 vrs 300 ml insulation

HoofRocks · 08-01-2014 5:22pm #1

Hi all.

if starting a new build again would you go with 250 or 300 ml pumped cavity. Builder suggests 250 would be adequate enough. 200ml in floor. Mhrv installed heat pump with underfloor triple glaze passive windows through out. Aiming for a3 rating.

My thoughts were to put in as much insulstion as possible but is there such a thing as too much?

BryanF · 08-01-2014 5:35pm

what do the calculations say?
why are you listening to the builder?

MicktheMan · 08-01-2014 6:13pm

HoofRocks wrote: »

My thoughts were to put in as much insulstion as possible but is there such a thing as too much?

It's not all about insulation; what's your AT target?

HoofRocks · 08-01-2014 6:26pm

MicktheMan wrote: »

It's not all about insulation; what's your AT target?

250 gives us the u value needed 0.13 Its not that im listening to the builder it was just a comment he made. If we want 300 ml he will put it in..havent looked at AT yet.

BryanF · 08-01-2014 6:42pm

HoofRocks wrote: »

250 gives us the u value needed 0.13 Its not that im listening to the builder it was just a comment he made. If we want 300 ml he will put it in..havent looked at AT yet.

what are your wall ties?

best to have all/any agreements/instructions in writing or even better - have all meeting with builder in front of your certifying architect;)

BryanF · 08-01-2014 9:32pm

Why would you be speaking to builder and not have considered air-tightness? Are you doing this build alone?

rockabaloo · 09-01-2014 1:30am

250mm is more than adequate.

fclauson · 09-01-2014 6:41am

rockabaloo wrote: »

250mm is more than adequate.

That depends on where your live - if it's Valentina Island South facing that May be over kill - if it's Birr on the north side of a hill with little or no winter insolation it might not be enough

Do the maths with a relevant local weather file

4Sticks · 09-01-2014 6:56am

Birr. Brrrrrr !

4Sticks · 09-01-2014 7:12am

250 / 300 thickness is a far less important consideration than ensuring thermal bridge free detailing. The risk of surface condensation increases with ever thicker layers of thermal insulation. You ask a far more complex question than it appears at first glance.

4Sticks · 09-01-2014 7:13am

rockabaloo wrote: »

250mm is more than adequate.

Glad you cleared that up.

HoofRocks · 09-01-2014 7:19am

BryanF wrote: »

Why would you be speaking to builder and not have considered air-tightness? Are you doing this build alone?

Spoke to him to see about prices for just starting the build. We want to have commenced before march to avoid the new regulations. Yes its a self build.

4Sticks · 09-01-2014 9:18am

HoofRocks wrote: »

We want to have commenced before march to avoid the new regulations.

but

better regulation and oversight of the sector is essential to ensuring a more sustainable industry and better protection for the consumer. I see these as critical reforms if we are to demonstrate that we have learned anything from the experience of the last two decades, said the Minister

aren't you keen to get with the plan ? What will you say to the person you will one day seek to sell your house to ?

rockabaloo · 09-01-2014 10:29am

4Sticks wrote: »

250 / 300 thickness is a far less important consideration than ensuring thermal bridge free detailing. The risk of surface condensation increases with ever thicker layers of thermal insulation. You ask a far more complex question than it appears at first glance.

I'd agree with this. Attention to thermal bridging ang go all out for airtightness. I reckon this would be a better time/money investment than taking a 250mm cavity out to 300mm.

Just my opinion but I reckon the figures would back it up pretty good.

4Sticks · 09-01-2014 12:05pm

Originally Posted by BryanF Are you doing this build alone?

HoofRocks wrote: »

Yes its a self build.

Take note professionals. This guy want's advice and information for free and is avoiding hiring one of us.

fclauson · 09-01-2014 12:17pm

4Sticks wrote: »

Take note professionals. This guy want's advice and information for free and is avoiding hiring one of us.

That's the point of this forum !!!!

4Sticks · 09-01-2014 12:19pm

but you also hired profesionals

fclauson · 09-01-2014 12:21pm

4Sticks wrote: »

but you also hired profesionals

True I did the AND option and not the OR

4Sticks · 09-01-2014 12:25pm

So - not just to you fc but to all....

It's obvious why the OP would see free advice as being

That's the point of this forum !!!!

Why should professionals oblige ?

BryanF · 09-01-2014 2:53pm

I feel your pain 4sticks, BUT Nobody is 'obliged' to respond...

4Sticks · 09-01-2014 3:36pm

Any advance on that - anyone ?

hesker · 09-01-2014 4:42pm

As a potential customer of the concerned professionals I value the awareness that the discussion in this forum provides. It increases my appreciation that I should engage the right professional when the time comes.

4Sticks · 09-01-2014 6:04pm

Well if you are building anything greater then 40m2 after March 1st you will have to by law engage a professional , whatever your appreciation of the issues.

To recap

1. the forum exists to provide free advice and information
2. professionals don't have to take part.
3. if they do some posters awareness / appreciation may increase.

Anyone care to add anything ?

BryanF · 09-01-2014 6:12pm

4Sticks wrote: »

Well if you are building anything greater then 40m2 after March 1st you will have to by law engage a professional , whatever your appreciation of the issues.

To recap

1. the forum exists to provide free advice and information
2. professionals don't have to take part.
3. if they do some posters awareness / appreciation may increase.

Anyone care to add anything ?

forum charter:

1.1 This board is intended for discussion of Construction & Planning issues, by fellow users, and as a place to openly exchange tips and advice for free i.e. no one must seek to gain personally, professionally or financially from their participation in the forum . It is not a consultancy service and it is strongly advised that you always appoint your own professional advisor(s). Be aware that being an open public forum you may not always get exactly the response you would hope for. You will find that there are plenty of posters who will help you here but if you don't like some posts or posters try to pass over them .

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The advice and opinions expressed on this forum are not those of Boards.ie Ltd. and the management accepts no responsibility for what is written and posted here.

4Sticks · 09-01-2014 6:23pm

Thank you . It seems increasingly that there is fair touch more of

to openly exchange tips and advice for free i.e. no one must seek to gain personally, professionally or financially from their participation in the forum

which is in fact being used a substitute for

it is strongly advised that you always appoint your own professional advisor(s)

As you yourself successfully drew out from the OP , this thread is a case in point.

So , apart from having professional suicidal tendencies (save for a nebulous hope that "awareness" be raised ) why would professionals continue to take part here ?

HoofRocks · 09-01-2014 7:24pm

I think everyone got a bit carried away there. I posted this as a general question, to get opinions and see what people thought. I wasn't looking for free professional advice. I certainly wasn't looking for the rules of using boards. This is a discussion form and that's what I was using it as.

And the OP is a she.

4Sticks · 09-01-2014 7:55pm

Sorry for calling you a guy.

Where do you want the discussion to go now ?

HoofRocks · 09-01-2014 8:17pm

4Sticks wrote: »

Sorry for calling you a guy.

Where do you want the discussion to go now ?

I think it has gone to its limit. Short answer I take from it is 250 is enough put the extra money into other elements

sydthebeat · 09-01-2014 8:21pm

do you know what the savings by not going from 250 to 300 are?

In order to analyse cost versus benefit, you need to know both values first.

rockabaloo · 09-01-2014 8:57pm

While that's true syd both you and I know that going from 250mm to 300mm cavity will only save tens of euros a year in most circumstances. You'll not even get close to saving hundreds. Not even close.

And 4sticks, you should relax a little. If you're attitude is an example of what to expect when engaging with a professional then it's quite obvious why people would rather throw the question out there in what is usually a friendly and open forum.

Best of luck with the build Hoofrocks. I'm not a professional but happy to give you my opinion based on my own experiences (as are most forum members) any time you may need help.

4Sticks · 10-01-2014 9:30am

You invert my point. My attitude here is borne from an OP NOT engaging a professional and coming here in lieu.

OP - be aware of one point in particular. Once a cavity exceeds 150mm width then that wall must be designed by a structural engineer.

fclauson · 10-01-2014 9:52am

4Sticks wrote: »

You invert my point. My attitude here is borne from an OP NOT engaging a professional and coming here in lieu.

OP - be aware of one point in particular. Once a cavity exceeds 150mm width then that wall must be designed by a structural engineer.

there is more to it than just that - you also need to design all your opes. and any steel needs to be designed

BobMcBob · 10-01-2014 10:07am

4Sticks wrote: »

You invert my point. My attitude here is borne from an OP NOT engaging a professional and coming here in lieu.

OP - be aware of one point in particular. Once a cavity exceeds 150mm width then that wall must be designed by a structural engineer.

I have spent a long time reading forum for help my own build. It has been invaluable to me and completely changed my build for the better. I have hired professionals, and actually hired some who I wouldn't have if it wasn't for this forum.
There may be some people who are looking for free advice but if they want to spend several hundred thousand based on Internet advice let them.

BmB

antiskeptic · 11-01-2014 12:30am

4Sticks wrote: »

Anyone care to add anything ?

There are professionals out there who'll rubberstamp you past the regs for an appropriate sum. Guys at the end of their working lives who've little to lose and are prepared to ride into the sunset for as long as their professional indemnity will carry them.

If a go it alone builder wants to build as unencumbered post-March as he is unencumbered now my bet is that it won't cost him more than a few dollars more than at present.

People won't ever stop being people. Especially not the way we do and enforce regs in this country.

4Sticks · 11-01-2014 1:45am

You mis understand my question.

You make your comments about some professionals and some builders out IRL*and future hope / no hope for building standards as you see it. Fair enough.

My question - if read back over the thread is - why would or should professionals take part in this forum by offering free advice to persons online to those who at the same time seek to avoid paying for it IRL*.

( in real life ) *

250 vrs 300 ml insulation

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