Deciding on Insulation specification for new build?

O

orcaborky

Registered User
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Hi All

Thank you for taking the time to read this. I am just about to submit my plans to the council, for a 2895sq ft open plan bungalow, well to be exact my architect is. He has been very helpful so far but after reading here I think it can be improved a lot? I intend to use a mechanical air ventilation system so I believe from what I have read air tightness is critical?

He has specified wall construction as follows:
100mm concrete block inner leaf, 60mm exp. insulation pinned to innerleaf, 40mm air cavitykept clear, 100mm blockwork outer leaf and render finish. Galvanised twist wall ties every 750mm horizontal and 450mm vertically and 225mm vertically at all unbonded jambs. 100 x 75 mm RC

I have been going through these treads for a few day and am looking for a definative answer on what is the best block wall, roof construction etc
If the plans are submitted as are can I change the insulation afterwards or does it mean re application?

If anyone can be of any help that would be great, I am planning on solar for the water heating and underfloor with either a condensed oil burner or geo for the space heating (along with the mechanical air ventilation system)

Thank you
 
These are my full specs

Hi Guys

I will type up the full specs below, What I am hoping to achieve from the house is minimal heat loss without going over board on costs, I will as mentioned before hope to have a mechanical air ventilation system, underfloor heating using either a condensed oil burner or geo for the space heating. I like the idea of block built. (the house is a basic rectangular bungalow that is open plan sitting/dinning/kitchen with the bedrooms off it ie no corridors as such.) Here goes the suggested spec.


FOUNDATION CONSTRUCTION:
900x300 mm concrete strip foundations to all external walls, with top surface a minimum of 600 mm below ground level. Concrete mix to 25 N 20 Agg reinforced as per Engineers instructions after excavation, 600x300 mm concrete strip foundations for all internal walls.


EAVES CONSTRUCTION:
H.R. PVC gutters or aluminium gutters on 200x5 mm PAO facia board with uPVC formed soffit and facia incorporating the equivalent of 10 mm continuous ventilation to roof space. PVC or aluminium facias, soffits, gutters and downpipes fitted in accordance with manufacturers instructions.


FLOOR CONSTRUCTION:
Power float finish 150 mm 20 N 20 concrete floor on 60 mm EPS insulation on radon membrane barrier on 50 mm sand blinding on 150 mm levelled and compacted hardcore base. DPC level (weathered)


WALL CONSTRUCTION:
100 mm concrete block inner leaf, 60 mm exp insulation pinned to innerleaf, 40 mm air cavity kept clear, 100 mm Blockwork outer leaf and render finish. Galvanised twist wall – ties every 750 mm horizontally and 450 mm vertically and 225 mm vertically at all unbonded jambs. 100x75 mm RC lintels to form opes with stepped DPC over all opes. DPC under cills to be turned up a back and sides. Vertical DPC to all jambs in external cavity walls. Ground floor DPC min 150 mm above finished path level. Cavity lean mix concrete infill to 225 mm below DPC level (weathered).


ROOF CONSTRUCTION:
Selected black roof slate on 50x38 mm laths on untearable sarking felt on prefabricated roof trusses @ 660 mm CC with hip girder trusses on hips as required bracing and fixings in accordance with manufacturer’s specification. 100x75 mm wall plate rag bolted every 1000 mm. 30x5 mm galvanised mild steel straps from uncut block in inner leaf of gable to tie 2 No, rafters and 2 No. joists at ceiling level, all straps min 2000 mm CC. 75x50 mm packing and noggin to underside of straps from gable wall between rafters and joists. 150 mm glass fibre insulation between joists. 12.5 mm foil backed plaster slabs to ceiling. 225x25 facia board. 18 mm soffit sheeting.
 
I have to say, if you are building in block, that is a very low insulation spec, and wouldn't imho, even meet minimum TGD's these days.........

I also don't think the foundation is up to much, either, but there again, that's imho.

What sort of standard(s)/performance are you aiming for, from the building ?

We're about to start a not-dissimilar bungalow in Co Dublin, and the spec is completely different........
 
galwaytt said:
I have to say, if you are building in block, that is a very low insulation spec, and wouldn't imho, even meet minimum TGD's these days.........

I also don't think the foundation is up to much, either, but there again, that's imho.

What sort of standard(s)/performance are you aiming for, from the building ?

We're about to start a not-dissimilar bungalow in Co Dublin, and the spec is completely different........
Click to expand...

I would be very interested in knowing you spec if you didn't mind. I just want to get the house built with the highest standard of insulation without going over board on cost ( ie keeping in mind the law of diminishing returns)
 
galwaytt said:
I have to say, if you are building in block, that is a very low insulation spec, and wouldn't imho, even meet minimum TGD's these days.........
Click to expand...

The TGDs dont mention figures or numbers when mentioning insulation spec.....They only mention detailing, i.e. how to avoid thermal bridgeing, and how to get the insulation envelope right. The TGDs dont even mention U values I think.


Building cavity walls is not the way forward.
Its very hard and takes a lot of builder skill to get the insulation right, mainly due to something called thermal looping.
Cavity walls came in 100 years ago with one aim in mind, to keep the rain out, its good at that. There is a lot of info on the web about the thermal flaws with cavity wall construction.

Building a new cavity wall house is a missed opportunity to choose a more modern building technique
 
orcaborky said:
I would be very interested in knowing you spec if you didn't mind.
Click to expand...

...no problem, but you do have to bear in mind I build non-masonry houses for a living.......and for a reason ! (BTDT !)....and I don't want to put off the Mods here by posting a link to me publicly. If mods are o.k. with it, I will.....

In general though, and if I use the example of the bungalow we're starting in Skerries in the not-too-distant future, the spec there is for A rating, with u-values of 0.165 for walls and roof (some vaulted rooms), but even a rating of 0.20 for walls is a good target, and to max out on the airtightness as well.
 
galwaytt said:
I have to say, if you are building in block, that is a very low insulation spec, and wouldn't imho, even meet minimum TGD's these days.........

I also don't think the foundation is up to much, either, but there again, that's imho.

What sort of standard(s)/performance are you aiming for, from the building ?

We're about to start a not-dissimilar bungalow in Co Dublin, and the spec is completely different........
Click to expand...

Is concrete built not better built? :)
To be honest I am not very knowledgeable about building but probably ignorantly I thought block was a better bet than timberframe? Longevity etc.

I really appreciate any information about the specification I should be asking for. Even a link to information on good specs would be brilliant.
 
Would this work?

Have been searching the web all day and this seems like a viable option?
Have to figure out the roof/floor etc etc now.

Render 15
Dense Block 100
Cavity >25
QUINN-therm 60 or Kingspan 60?
QUINN-lite B5 215
Insulated Plasterboard

The more I learn the more I find out I know nothing :)
 
orcaborky said:
Is concrete built not better built? :)
To be honest I am not very knowledgeable about building but probably ignorantly I thought block was a better bet than timberframe? Longevity etc.
Click to expand...

you are right, from a structural and longevity point of view, concrete is a great option.

You could look at icf's (insulated concrete forms), google them.
 
orcaborky said:
Is concrete built not better built? :)
To be honest I am not very knowledgeable about building but probably ignorantly I thought block was a better bet than timberframe? Longevity etc.

I really appreciate any information about the specification I should be asking for. Even a link to information on good specs would be brilliant.
Click to expand...
LOL - you've been reading too much of t'internet !

The longevity of our system - - is the exact same as masonry construction, and is certified to be so.

As for 'better built' slogan - the problem is the quality of on-site practice, and this is why MMC - (Modern Methods of Construction) - i.e. factory built houses like ours, perform better, more easily.

Leo said:
In the context of providing further detail to this dicsussion, post away.
Leo
Click to expand...
Our std build model, based on using a lined 130mm panel, will give you a highly airtight structure - without membranes - and a u-value of 0.20. Our thicker panels can give, with appropriate lining (insulated board, for example), of 0.15. The limit is dictated to by your budget, as distinct from the product. In particular, the airtightness properties of our houses, currently under construction/finishing by clients, without any membranes, have been coming in around 1.6/1.03 and even 0.09 m3/hr/m2. And, being solid walls, you can't accidentally damage the airtightness, either (say, with a knife, etc).

Then there's cost: we started, for example, a 1400sq ft bungalow on Tuesday 18th May, when we walked on to the site. We spent the first day setting up, surveying, sole plates, putting in crane, some scaffold, etc. On Wednesday morning, around 9.30, we commenced build. We finished the entire structure (to our extent), including the felt and counerbattens on the roof, around 15:00rhs on Monday 24th May. 4 days of on site work to put up the entire house. Fully insulated, highly airtight, including the rood and the attic (floored/insulated as well). The house is ready for internal and external finishes, immediately. We had all the conduits in the wall, for the electricians, it had Open Web Joists to accomodate HRV etc etc. The point I'm making is this: less time on site, because so much is done in the factory can give you a better home, more quickly. And, ultimately, and I know I am, I'm paid by the hour. So, proportionately, my price has a much lower labour content than 'conventional'. Which means that I'm putting more money into materials. Which is good for the home owner, and will be reflected in his energy bills. I've no problem telling you how much: €260 - € 295/sq , dependant upon design/level of complexity. I find that efficiently designed (simpler) buildings are cheaper, per sq m, to build, over ornate ones - it's not the size per se that's the issue. Finished costs to builders finish I'm advised by a local contractor, about €850/sq m (c/w UFH, solar panels, HRV, etc etc) and upwards (like everything, the sky is the limit when it comes to finishes.....)

orcaborky said:
Have been searching the web all day and this seems like a viable option?
The more I learn the more I find out I know nothing :)
Click to expand...
BTDT, I know how you feel.

Whiskey said:
you are right, from a structural and longevity point of view, concrete is a great option.

You could look at icf's (insulated concrete forms), google them.
Click to expand...

There's nothing special about the performance of 100mm conc block, load-wise - our system, for example, out-performs concrete block in a simplistic load-bearing test,....here comes the science bit ....tested at 337.2kN/m, with a long term design value of 42kN/m so concrete block construction is not stronger.
As mentioned also, ours is certified to perform no less than the life of equivalent masonry.

In general, for example, in Scotland, with a wetter climate, and higher windloads than we do, 70% of all new builds are timber-based.....so there is no need need for concern about the longevity.

ICF. Hmm, I'm afraid my experience (having worked on them), is that the biggest issues is that the quality is entirely site-subjective, and is influenced by our (wet) climate during the actual coarse of construction.

And of course, ICF is a wall system - you still need a roof - and we've had the (?) fortune to have had to roof several ICF's.......

.....I'd be happy to pass on contact details to OP of an ICF (self) builder if he wants to check his experience directly.

Sorry for the lengthy post.
 
Brilliant post thank you, one question though, can you put blockwork ie stone cladding to the outside as a lot of the wood I have seen seems to age quickly and needs maintenance, it is my intention to keep as maintenance free as possible.

Also will I need to change the house specification prior to submitting my plans if I want anything different as regards house spec., for example if I wanted to change from:
100 mm concrete block inner leaf,
60 mm exp insulation pinned to innerleaf,
40 mm air cavity kept clear,
100 mm Blockwork outer leaf and
render finish

to:
Render 15
Dense Block 100
Cavity >25
QUINN-therm 60 or Kingspan 60?
QUINN-lite B5 215
Insulated Plasterboard
 
Orcaborky - a few things: your plans, for planning purposes: it is irrelevant what method of build you propose to use. Planning is only concerned with the 'appearance' and details of location/type/size/style etc - it has nothing to do with the technology of build. You can put in your application based on concrete block/whatever, and build it from whatever you like, so long as it looks like what you have planning for. No need to get hung up on that, at this stage. No need to change anything on your existing plans, for the planning process.

The technical issues of compliance with building performance are not part of the planning application process.

Now, with regard to your point aobut timber houses in general, I think you are mis-understanding timber-based construction such as ours, completely ! Timber based buildings, like our SIP panels, don't look like log cabins, or anything. In fact, they look remarkably..........'normal' !

Some examples of 'standard' house types we have done:






...and then they start getting.....elaborate !...









So, you can see why their durability is the same as anyting else - all the finishes are very standard, widely used, and locally available.

Here's a house under construction, just before the roof is put on. You can see all the (insulated, airtight) walls are up, even the attic is in (floored), and all interior walls fitted as well (insulated). The roof took one day to fit, and then the owner had a block layer put blocks around the outside. This house is about 2500sq ft, and was built in 6 days.



I hope this sheds some light on your options - sometimes, it's too easy to get 'blinded by science'.
 
I am now seriously interested in your building procedures, just a few questions. Please excuse if they sound dumb but it would make me a lot more confident and sure.

What are the chances of dry rot or wood worm?
If a water leak internally is not spotted quickly can it cause major problems structurally?
Can I hang pictures/brackets etc on internal walls (ie are they strong enough)?
Sound proofing issues?
What is the fire risk (is it greater than concrete built)?
Wood tends to move when heated or cooled can this cause cracks?
More inviting for mice?
Is the possibilities of mold on wood is higher than on concrete?
Do the treatments on the timber have a lifespan before they are not as effective?
How much is timberframe cheaper than concrete in general?

I am sure that these issues have all been resolved and I probably have been misinformed by the Concrete camp! :)

Thank you again for all your help.
 
BLOCK IS DEAD LONG LIVE TIMBER???

Just check out the modern building regulations, they are so strict that rot, fire risk and decay are no longer serious issues to be considered. Warranty providers certainly don’t consider them problems and neither should you.

The fact that so many developers choose timber frame nowadays is testament to the fact that for the resale market your choice makes no difference whatsoever.

Just remember a standard 140mm timber frame wall will achieve a Uvalue of around 0.24 — on a wall thickness less than half that of its blockwork equivalent.

It is going to be more difficult for blockwork homes to meet the future energy efficiency requirements without resorting to greater wall thicknesses.

Cheers
Bren
 
Sorry, been away in UK all week, so if this short-fire reply is ok...see in bold, below...

orcaborky said:
I am now seriously interested in your building procedures, just a few questions. Please excuse if they sound dumb but it would make me a lot more confident and sure.

What are the chances of dry rot or wood worm? None, as ours is a sealed (not a 'closed') panel system, and has only a fraction of timber content of std TF. Remember that dry rot and related issues generally, are not usually the fault of the materials, but rather that of the quality of the installation, and construction details. For example, if one of our houses was flooded, to a depth of 1m, it would have no effect, once the water level went back down. By dint of a solid, sealed wall, with no air passages therein, there is nothing inside it to either contain water, nor, by extension, to dry out.
If a water leak internally is not spotted quickly can it cause major problems structurally? Water services are fittied in the exact same manner as a conventional house, through provided service areas, so the short answer is that your leak will be spotted just as quickly as in any other build. And, like the previous comment, there is no reason, erected properly, that it should affect the house structurally.
Can I hang pictures/brackets etc on internal walls (ie are they strong enough)? Our walls, by being a completely solid, laminated, timber-faced system, are actually stronger. You can put in a screw, anywhere. You can hang heavy items such as your kitchen units and your stairs - at ANY position - and all without using any wall plugs/toggles/ etc etc No more loose curtain rails or blinds, either.........
Sound proofing issues? Our walls have been acoustically tested and are, in general quieter than both timber frame AND conventional build.
What is the fire risk (is it greater than concrete built)? Our walls have to (and must, by law) meet the same standards as all other types of build.
Wood tends to move when heated or cooled can this cause cracks? This can happen in conventional timber frame, especially if using native (i.e. Irish) timber, as the system is nailed together.....as wood dries over time, nails can sometimes get loose. Our system does neither, and all our junctions are screw joints - not nailed. Screws don't 'relax' over time.
More inviting for mice? No, there is no void in our product for them to get into, and the insulation will not support.....life !
Is the possibilities of mold on wood is higher than on concrete? Be aware that there are two types of 'mold' - that from the surface, and that from within. Surface mould is usually caused by high levels of humidity and poor ventilation, and can be found in any type of house build. Some surface mould is caused by cold surfaces, which may indicate a heat loss path (cold bridge), and this is more a feature of concrete construction than any wood one. Again, this is a non-issue in our product, as it is a sealed, solid, laminated wall. There is ZERO interstitial condensation in our product, at any time of the year, in our climate. This is what our product has been tested and accredited to. Block and timber frame, on the other hand.........can have this problem, as they can have an interstitial condensation point.
Do the treatments on the timber have a lifespan before they are not as effective? Treatments ? Please elaborate......
How much is timberframe cheaper than concrete in general? Timber as a material, is not cheaper, per m3, it is more expensive. What you need to do is to calculate your entire build, and see what the overall difference is. Our product, by a recent calculation of a local builder here, over the entire house (including foundations and to bring it to finish level), came out at +1.4% over 'conventional'.

I am sure that these issues have all been resolved and I probably have been misinformed by the Concrete camp! :)

Thank you again for all your help.
Click to expand...

Like everything, there's horses for courses and all that !
 
I must admit I am very impressed with the SIP system and after talking to Sip Energy I will be visiting them in the next week or so. They answered all my questions so far. I was just wondering if anyone here has had a SIP home built and what was their experience?
It is quiet a turnaround for me (was very much a block build concrete fan) and an eye opening journey. I still have a lot to learn but I would just like to thank everyone who has contributed and shared their knowledge on these forums as I would have never known about all the alternatives available. It really is "Horses for courses" depending on your individual circumstances.
 
orcaborky... did you go forward with a SIP build? If yes, how did it go for you?
 
Hi,

Can anybody tell me the difference between a closed TF house and a SIP house. Are there advantages of one over the other?

Thanks
 
Muffet said:
Can anybody tell me the difference between a closed TF house and a SIP house. Are there advantages of one over the other?
Click to expand...

Please don't drag this thread off-topic. Post a new thread if there isn't already a discussion on this.
Leo
 
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