bewildered by my architect

Bobbiblu

Hi all,

I'm still undecided as to what construction method to use in my new build. I'm hoping (like we all are no doubt) to strike a balance between a well insulated, low energy house and a budget.
I've got a very simple design, directly south facing with the majority of glazing on this side plus all of our main living space. I'm certain about a couple of things - air tightness, MHRV, solar for DHW, and high quality low u value glazing....but as I said I'm still considering build types - I have no experience with any form of construction and I'm not blessed with any family members who have either, so while chatting with my architect yesterday re construction methods he told me that the best insulated house (he's apparently done a lot of research on this) for the least amount of money (don't get me wrong, I'm not looking for a "cheap" house - I'm looking for the best way to spend the budget) with a u value in the walls of .2 was as follows (excuse the inches - his choice not mine)

4 inch inner leaf,
six inch cavity filled with silver bead blown insulation
and 4 inch outer leaf.
nothing else!!

Does this sound right to you guys?? Now, like I said I've no first hand knowledge of any construction method but from what I've read here and in other sources this just seems too simple too be true!! he says the silver bead will serve two functions - reflecting heat back in to the house during winter and reflecting it into the atmosphere during the summer months preventing the house from getting too hot. When I asked about moisture considerations in the cavity, he said that silver repels moisture so moisture wouldn't be a problem either and that plaster on the outside will prevent any moisture getting in any way. He reckoned this is a far better method ( as regards ratio of insulation level to money spent on achieving a u value of .2 in walls) than any form of timber frame, steel frame, ICF etc and that bonded bead is far better than any form of Kingspan et al insulation boards that are available - he wasn't even keen on my suggestion of quinn lite blocks or similar - I have an uneasy feeling about this one so what do you guys say???

Sorry for the long rant.....like I said I'm bewildered by it all so thought it best to consult the real professionals

topcatcbr

I agree with you. I would be a bit concerned with this. It would probably be cheep but.

1. It does not deal properly with Cold bridging. Which could lead to mould growth.
2. 6" (150mm) is a large cavity and would require engineers structural detail.
3. if the wall thickness is increased then so must the foundation.

Link to product
http://www.warmfill.com/warmfill_information.htm

RKQ

I'm assuming this is a new house, granted after 30th June 2008, or it won't be substantially complete before 30th June 2009.

So, I assume you will require a BER Cert from a qualified SEI registered BER Assessor with PI Insurance. I suggest you retain an Assessor with experience in the Building industry - preferabably an experienced Architectural Technician. The Assessor can assess all build methods and provide you with all the options.

I am in no way being disrespectful to your Architects professional opinion. But if we assume that foil beads repel moisture then we must assume they repel moisture in all directions. Being a circular bead if wet they could repel water into the inner leaf. ( They can't repel moisture in one direction and be pre-programmed to know where the outer leaf is!:D)

sinnerboy

Firstly , must say that I have never used a product like this - but that is not to say I would not

Make sure the product used is certified ( IAB/BBA) - like this one

http://www.nsai.ie/modules/certificates/uploads/pdf/IAB050191.pdf

Some of the Social housing in the Ballymun Regeneration Project is constructed using a similar spec - 200 cavity . I tried to find a PDF link just now , but can't find it , sorry .

Note the requirement that cavities wider than 110mm will require certification by a STRUCTURAL ENGINEER ( only )

Stepped dpc's should be used over openings as per any cavity wall

You have no reason to be bewildered

Dr. Nick

31 Days in June this year? Excellent!

Bobbiblu

topcatcbr wrote: »

I agree with you. I would be a bit concerned with this. It would probably be cheep but.

1. It does not deal properly with Cold bridging. Which could lead to mould growth.
2. 6" (150mm) is a large cavity and would require engineers structural detail.
3. if the wall thickness is increased then so must the foundation.

Link to product
http://www.warmfill.com/warmfill_information.htm

Cheers for that topcatcbr, will do a bit more research and see what I can come up with, will be back here again with more questions no doubt!

RKQ wrote: »

I'm assuming this is a new house, granted after 31st June 2008, or it won't be substantially complete before 31st June 2009.

So, I assume you will require a BER Cert from a qualified SEI registered BER Assessor with PI Insurance. I suggest you retain an Assessor with experience in the Building industry - preferabably an experienced Architectural Technician. The Assessor can assess all build methods and provide you with all the options.

Hi RKQ, thanks for your input. Yes this is a new build and I see an ever increasing amount of recommendations for retaining a BER Assessor so will definitely try source a good one in the locality - I suppose I thought my architect would have all the info I required but I guess that's inexperience on my part.

RKQ wrote: »

I am in no way being disrespectful to your Architects professional opinion. But if we assume that foil beads repel moisture then we must assume they repel moisture in all directions. Being a circular bead if wet they could repel water into the inner leaf. ( They can't repel moisture in one direction and be pre-programmed to know where the outer leaf is!:D)

good one... didn't look at it like that....

sinnerboy wrote: »

Firstly , must say that I have never used a product like this - but that is not to say I would not

Make sure the product used is certified ( IAB/BBA) - like this one

Hi Sinnerboy, thanks for the good advice.

sinnerboy wrote: »

Note the requirement that cavities wider than 110mm will require certification by a STRUCTURAL ENGINEER ( only )

Noted!

sinnerboy wrote: »

Stepped dpc's should be used over openings as per any cavity wall

Noted again thank you.

sinnerboy wrote: »

You have no reason to be bewildered

In my defence, this minor scenario has been the latest in long line of frustration-inducing episodes with my architect - I expected more of him really and that's a fault on my part and I guess my frustration got the better of me yesterday....but thanks for the reality check

sinnerboy

Bobbiblu wrote: »

In my defence, this minor scenario has been the latest in long line of frustration-inducing episodes with my architect - I expected more of him really and that's a fault on my part and I guess my frustration got the better of me yesterday....but thanks for the reality check

I wish you well , hope the frustrations ease . But if you have a look at the IAB cert - in particular the table of cavities / u values you'll see that your architect has proposed a sound spec

Slig

The only thing I see wrong with the system is the air proofing.
This seems like a "modified" version of the traditional cavity wall. The cavity wall has worked grand for years, the lower U-values and breathability are tried and tested but by modifying it to incorporate better insulation and removing circulating air we dont really know what will happen. There may be nothing wrong with it but I would prefer to see an air proof membrane on the inside of the blockwork (we can assume that the cavity fill insulation is providing an air proof barrier) and a structural inner leaf (150 or 215 blockwork, lightweight will give you a better U-value).

The 300mm cavity wall is structurally weak with only a 100mm cavity, stretching it to 150mm is in my opinion not sound. The wall will also require extra wall ties but most other issues can be resolved such as cills etc.

At the end of the day we are all pioneering these new systems, nobody really knows what will work and what wont. Try abit of research and if your not comfortable with the advice your getting try somewhere else. Seek certification and guarantees on any products you use.

jonnyj

OP your house is simple in design and south facing! How about forgetting traditional construction for a minute and look into Passive construction. There are plenty of companies out there that can help with information etc. Its the future and will become the standard once we catch up with the rest of europe.