Cost of >150mm cavity + aerated autoclaved blocks

heavydawson

Hey all
I'm at the planning stage of a self-build at the moment, and after reading the comments here and elsewhere, I've started to focus my attention on insulation and airtightness ahead of choosing heating systems.
I've spend a few hours each night for the last week going over the L regs for 2008 and the new 2011 regs that are due to take effect on Dec 1st.
As I'll be submitting the planning application before then, I don't have to worry about meeting the 2011 regs, however I actually would like to try and meet them if possible.

From all I've gathered regarding insulation, my targets for the ~3100 sq. ft. house I'm planning boil down to the following basics:
Air-tightness <3m3/hr/m2
Roof U 0.14
Floor U 0.15
Wall U 0.14 Widened Cavity Full Fill >=150mm cavity likely, autoclaved aerated blocks on inside leaf, wet plaster finish
Windows <=1.6u 20mm air gap windows (double/triple-glazed)

These are the targets, and they'll be adjusted depending on what I can afford.

What I'd like to know is:
1. Whats the %increase in cost for choosing 150mm over 100mm, or 200mm over 150mm? Does anybody have a rough idea?
2. Does anyone know what the percentage increase in cost of autoclave aerated blocks over a standard concrete block?

Feel free to make suggestions regarding the makeup of the cavity wall + insulation, and I'd particularly like to hear from people who've opted for > 150mm cavities, what type of fill they've used, and how satisfied they were with the design/workmanship afterward.

fclauson

Hi

I would suggest you employ a QS - the best money I ever spent. Using Aerated blocks prooved cost prohibative - and they are only equal to about 25mm of bead - so if you are going for a wider cavity then just add 25mm of bead and use regular conc block

You just need to think about what goes along the bottom of the walls to stop thermal bridge to ground - there are some bespoke blocks - or you can use just a row or two of aerated blocks before the conc blocks

hope that helps

search my other threads where I talk about the above

heavydawson

fclauson wrote: »

Hi

I would suggest you employ a QS - the best money I ever spent. Using Aerated blocks prooved cost prohibative - and they are only equal to about 25mm of bead - so if you are going for a wider cavity then just add 25mm of bead and use regular conc block

You just need to think about what goes along the bottom of the walls to stop thermal bridge to ground - there are some bespoke blocks - or you can use just a row or two of aerated blocks before the conc blocks

hope that helps

search my other threads where I talk about the above

Thanks for the tips, I'll definitely be employing the services of a QS. Have you any tips/ideas/suggestions for figuring how to build a wall to meet a particular u-value? I can seem to find a hard-and-fast way to determine:
1. cavity width
2. full fill insulation material
, in conjunction with standard 100mm concrete blocks, to achieve a u-value of 0.15 for the walls.

sas

heavydawson wrote: »

Thanks for the tips, I'll definitely be employing the services of a QS. Have you any tips/ideas/suggestions for figuring how to build a wall to meet a particular u-value? I can seem to find a hard-and-fast way to determine:
1. cavity width
2. full fill insulation material
, in conjunction with standard 100mm concrete blocks, to achieve a u-value of 0.15 for the walls.

Lets take it back a step.

Who decided that 0.15 is wall u-value target and how did they come to that conclusion?

What build up did they suggest in order to achieve this?

heavydawson

sas wrote: »

Lets take it back a step.

Who decided that 0.15 is wall u-value target and how did they come to that conclusion?

What build up did they suggest in order to achieve this?

Fair point sas. I'm the one that is trying to achieve that spec. I've spent the last few weeks versing myself in the L Build Regulations 2008/2011, and come up with a with the high-level spec I mention in the first post.
I'm now trying to figure out how I can achieve the target of 0.15 for the walls on the assumption I'll be using a full fill cavity with standard 100 mm concrete blocks for the outer and inner leaf

sas

heavydawson wrote: »

Fair point sas. I'm the one that is trying to achieve that spec. I've spent the last few weeks versing myself in the L Build Regulations 2008/2011, and come up with a with the high-level spec I mention in the first post.
I'm now trying to figure out how I can achieve the target of 0.15 for the walls on the assumption I'll be using a full fill cavity with standard 100 mm concrete blocks for the outer and inner leaf

Before you go employing a QS, employ to an Arch Tech.

The problem here is that as non construction professionals, you and I are not necessarily able to determine all the factors and how they interact with each other.

You can determine the u-value based on the thickness and thermal conductivity of the wall materials. Do you know how to factor in the bridge effect of wall ties? I know I don't.

What about the effect of how you mount your windows?

You need to assess the building as a whole with each factor adjusted to achieve the best performance in the most cost effective way.

As I read over on the fitness forum...

"If you're not assessing, you're guessing"

BryanF

heavydawson wrote: »

Thanks for the tips, I'll definitely be employing the services of a QS. Have you any tips/ideas/suggestions for figuring how to build a wall to meet a particular u-value? I can seem to find a hard-and-fast way to determine:
1. cavity width
2. full fill insulation material
, in conjunction with standard 100mm concrete blocks, to achieve a u-value of 0.15 for the walls.

employ an arch tech with passive house experience and get your building modelled in PHPP, also get a provisional BER done.

when you say your at planning stage has your planning application been made?

heavydawson

BryanF wrote: »

employ an arch tech with passive house experience and get your building modelled in PHPP, also get a provisional BER done.

when you say your at planning stage has your planning application been made?

Planning application has not been submitted, but is due to be in the next week based on a site purchase stipulation from site vendors. Do you guys know what it would cost to get the house modelled in PHPP by a pro so I could get an idea of what I need structurally to achieve the targets I'm reaching for?

BryanF

I wouldn't like to say with seeing the design, but IMHO probably less than the price of your planning application.
Really where it costs extra is when you have to spend time tinkering with the program and the design to optimise the energy consumption.
Next week for application.. if your floor plan is quiet large or sprawling single storey(excuse my turn of phrase) you should ideally get this done first before submitting planning

BryanF

take the title block and your particulars off the drawings (maybe try to put a water mark across them saying copyright) and give us a look

heavydawson

BryanF wrote: »

take the title block and your particulars off the drawings (maybe try to put a water mark across them saying copyright) and give us a look

Attaching plans with stripped title block and copyright notice.

BryanF

heavydawson wrote: »

Attaching plans with stripped title block and copyright notice.

Id recommend you get the phpp done prior to planning just to get an appreciation of what you need to do to insulate and keep your heating/energy to a minimum. it would be worth while seeing what could be rationalised in the design at this stage, while you have the chance..

BryanF

I know this isn't why you posted the drawings, but there's a lot of corridors, and space in your current plan...
the utility is on the south side of the building, which is maybe not the best use of all that light and probably outlook. the north end of the landing on the first floor could probably have the doors adjusted slightly and become a slightly smaller study, and by moving the downstairs wc under the stairs you could remove that east single storey block.
this might allow the utility to move more to the east side and maybe even move a reduced sunroom into the centre of the house removing the west single storey block.
again apoligies for completely overstepping the mark from what you original wanted to know, but if those changes or something similar was achieved, that's a possible 45msq reduction or 1/6 of the total build, meaning you could go to passive standards for the same budget. saving you substantially on your lifetimes energy bills...

heavydawson

BryanF wrote: »

I know this isn't why you posted the drawings, but there's a lot of corridors, and space in your current plan...
the utility is on the south side of the building, which is maybe not the best use of all that light and probably outlook. the north end of the landing on the first floor could probably have the doors adjusted slightly and become a slightly smaller study, and by moving the downstairs wc under the stairs you could remove that east single storey block.
this might allow the utility to move more to the east side and maybe even move a reduced sunroom into the centre of the house removing the west single storey block.
again apoligies for completely overstepping the mark from what you original wanted to know, but if those changes or something similar was achieved, that's a possible 45msq reduction or 1/6 of the total build, meaning you could go to passive standards for the same budget. saving you substantially on your lifetimes energy bills...

No bother at all. I appreciate any feedback I can get to be honest. Will take what you said into consideration. Thanks for the suggestions!

heavydawson

BryanF wrote: »

I know this isn't why you posted the drawings, but there's a lot of corridors, and space in your current plan...
the utility is on the south side of the building, which is maybe not the best use of all that light and probably outlook. the north end of the landing on the first floor could probably have the doors adjusted slightly and become a slightly smaller study, and by moving the downstairs wc under the stairs you could remove that east single storey block.
this might allow the utility to move more to the east side and maybe even move a reduced sunroom into the centre of the house removing the west single storey block.
again apoligies for completely overstepping the mark from what you original wanted to know, but if those changes or something similar was achieved, that's a possible 45msq reduction or 1/6 of the total build, meaning you could go to passive standards for the same budget. saving you substantially on your lifetimes energy bills...

BryanF, I'm attaching another design we came across only last weekend. It's too big for our needs, but I'm curious to see what you think of room orientation based on your comments about our current plans. I quite like the idea of using more of the south facing aspect of the house for living space, but the one change I'd make to this new plan is to move the family room from the back of the kitchen to the right-hand side of it (west in our case)

BryanF

heavydawson wrote: »

BryanF, I'm attaching another design we came across only last weekend. It's too big for our needs, but I'm curious to see what you think of room orientation based on your comments about our current plans. I quite like the idea of using more of the south facing aspect of the house for living space, but the one change I'd make to this new plan is to move the family room from the back of the kitchen to the right-hand side of it (west in our case)

that's some yoke:D, I don't know where to start. sounds like your not that happy with your current design? all you can take from this drawing is the orientations are all right for the general room locations. presuming south is up the page that is..

sas

That alternative design has several rooms with 3 external walls. That's asking for trouble in my opinion.

My home was designed to be passive.

Downstairs North (front)
- Utility
- WC
- Hall
- Office\Playroom

Downstairs South (Rear)
- Openplan kitchen\diner
- Living room

Upstairs North (front)
- Master Ensuite
- Bathroom
- Landing
- Spare bedroom

Upstairs South (Rear)
- Master bedroom
- Child No1 Bedroom
- Child No2 Bedroom
- Jack&Jill Ensuite.

The principle being that the least frequenty occupied rooms are on the cold side of the building.

heavydawson

Met with BryanF over the weekend who gave me some great pointers, and also spoke with a kitchen designer yesterday who basically told us we'd be idiots if we didn't re-orient the living areas (as did BryanF).
The result:
An all-nighter last night with Sketchup to fix the downstairs layout, and tweak the dimensions upstairs.
Fired off the updated plans to our planner with layout and dimensions pre-decided to save her time
I think the downstairs is as good as I'm gonna get it and keep the missus happy, but the upstairs might change still:

* Flip the master bedroom upstairs so it faces south.
* Get rid of the ensuite in on the east (left) wall of the house, move the adjoining wardrobe in its place, and use the current wardrobe space for a large hall-accessible linen space/mhrv store.

Please don't judge the size of the island in the kitchen. It was sized that way to show how big it COULD be with a 1.1m alley the entire way around it.
Also, I've only put one window in these plans, as it's the only major new addition glazing-wise. I'm still not sure if I can get a structurally sound corner window setup that size. Hopefully :-)

I'd love to bring the utility and downstairs WC into the fold of the main building, but that ain't gonna happen with the current footprint.

Feel free to comment on the new design, good or bad, and thanks for all the help so far.

musclesmcginty

Other than the obvious - what suppliers (or manufacturers) are doing these Aerated Blocks in Ireland now (2012)?

Getting it hard to find an alternative to the market leader.