internal insulation and cold bridging

HoofRocks

Recently had our BER done. He suggested we use board insulation in the cavity and internal insulation on the walls. After much reading here on boards and other forums we concluded it would be best to have a wider cavity and pumped bead insulation. I've went back with this and he is going to look at this option however he said his concerns are how to prevent cold bridging if we do not have internal insulation.

For all of you who have gone with the wider cavity and keeping your insulation all together have you experiences any issues with this?

Any feedback much appreciated.

Outkast_IRE

HoofRocks wrote: »

Recently had our BER done. He suggested we use board insulation in the cavity and internal insulation on the walls. After much reading here on boards and other forums we concluded it would be best to have a wider cavity and pumped bead insulation. I've went back with this and he is going to look at this option however he said his concerns are how to prevent cold bridging if we do not have internal insulation.

For all of you who have gone with the wider cavity and keeping your insulation all together have you experiences any issues with this?

Any feedback much appreciated.

you reduce cold bridging by having someone qualified draw up the necessary details, which you then must ensure are carried out on site.
I believe this falls into the remit of an architect or architectural technician.

If your BER advisor doesn't understand this then I am wondering is it out of touch with the methods used today. Internal insulation would be my last choice in a new build.

HoofRocks

So my architect should provide this? What are the necessary details?

Outkast_IRE wrote: »

you reduce cold bridging by having someone qualified draw up the necessary details, which you then must ensure are carried out on site.
I believe this falls into the remit of an architect or architectural technician.

If your BER advisor doesn't understand this then I am wondering is it out of touch with the methods used today. Internal insulation would be my last choice in a new build.

richj

Internal "Dry Lining" insulation will not prevent cold bridging. Go with the wider cavity and pumped insulation.
If you really look into internal insulation you will find out why it is never used in climates that are much colder than ours, there is a risk of mold and mildew build up between the internal wall and the internal insulation if used in conjunction with cavity insulation due to the location of what is know as the dew point. If I was building again I would go for an external insulation system, this is the only way to completely remove the risk of cold bridging.

sydthebeat

As above, Wider cavities will do more to reduce thermal bridges than internal dry lining.

I'm not quite sure what your engineer is in about.

BryanF

HoofRocks wrote: »

he is going to look at this option however he said his concerns are how to prevent cold bridging if we do not have internal insulation.

it would appear this person is a BER assessor only and not qualified to discuss your wall type/construction project any further than the BER calculation

richj

From my experience from working in the insulation business there are quite a lot of BER assessors that are not qualified to discuss construction but think they can, the only person I would take advice from is a good architect.
P.S. The same goes for Insulation "Experts" (i.e. salesmen for insulation companies), they are, in most cases, only interested in selling their own products and rarely will they suggest something that they cannot benefit from.

HoofRocks

Thanks for all the advice folks.

prewtna

my preference is for all the insulation to be in the same 'plane' and not to split it into two. as above dew point etc is the problem.

maybe changing the topic slightly, (mods feel free to send me packing on this) could i ask a question - i am torn between two options as a default for recommendations / advice to people and am interested to hear other peoples take on it.

the cavity wall is an incredibly simple device for dealing with heat loss and preventing moisture ingress particularly in our climate when external leafs are wet for weeks on end.

what i cannot decide is whether its better to just pump the cavity or bump up the board spec in the cavity and retain an air gap. both options allow the window to be (more or less) in the same plane as the insulation. the reason i say this would be my concerns in relation to ensuring the continuity of the pumped bead within the cavity and if there are any areas where its not pumped as it should be, then the possibility of water tracking in through the wall.

perhaps i am over-analysing the issue. anyone with any views / rebukes?!

BryanF

prewtna wrote: »

what i cannot decide is whether its better to just pump the cavity or bump up the board spec in the cavity and retain an air gap.

pumped if the the contractor is not selected & trusted by you the certifier

richj

A bump up in spec of the board insulation is and always will be a better solution than pumping the cavity, you can get much better U Values using high grade board insulation however the down fall of this method is the fitting. You are relying on a block layer to fit this insulation and to cut it properly around opes, you also need to have the board fitting tightly to the inner leaf so the pointing on the block work needs to be tidy within the cavity also. Where the pumped insulation option is better is that, if installed correctly, there will be no gaps in the insulation within the cavity. There are pro's & con's with both types. FYI, as I said before I worked in the insulation business for years and I had my walls pumped.

fclauson

richj wrote: »

..... you also need to have the board fitting tightly to the inner leaf so the pointing on the block work needs to be tidy within the cavity also. ...

I cannot remember the exact number - but it was horrific - perhaps something like a 5mm gap could lead to a 90% degradation in performance !!
Hence pumping is the way to go

what I wish I had done was pour - that is when as the cavity was being closed pour and temper the bead like one does concrete - thus ensuring a really really good fill of the cavity

MicktheMan

fclauson wrote: »

I cannot remember the exact number - but it was horrific - perhaps something like a 5mm gap could lead to a 90% degradation in performance !!

6mm;)

rodzer

quote "From my experience from working in the insulation business there are quite a lot of BER assessors that are not qualified to discuss construction but think they can, the only person I would take advice from is a good architect."
Or perhaps Architectural Technicians/ Technologists who may also be BER Assessors

fclauson

MicktheMan wrote: »

6mm;)

whats a mm between friends

richj

rodzer wrote: »

quote "From my experience from working in the insulation business there are quite a lot of BER assessors that are not qualified to discuss construction but think they can, the only person I would take advice from is a good architect."
Or perhaps Architectural Technicians/ Technologists who may also be BER Assessors

Thats why I said "quite a lot of BER assessors" and not all, but I see what you mean :cool:

Don't get me wrong I have met some very good BER assessors and some were fully qualified architects, but there are just as many bad assessors that jumped on the BER bandwagon when the downturn in construction occurred and some of the "advice" they were given uninformed people was crazy.

timmy4u2

richj wrote: »

Thats why I said "quite a lot of BER assessors" and not all, but I see what you mean :cool:

Don't get me wrong I have met some very good BER assessors and some were fully qualified architects, but there are just as many bad assessors that jumped on the BER bandwagon when the downturn in construction occurred and some of the "advice" they were given uninformed people was crazy.

Why are BER assessors giving advice?

richj

the unfortunate part is that some people don't know any better, and if I recall correctly it is part of the BER assessment that advice is give on how to increase your homes efficiency.

Outkast_IRE

timmy4u2 wrote: »

Why are BER assessors giving advice?

Because as part of doing a BER they need to recommend ways to improve the the BER score you got. Its part of the report they must do for every house.

And I would imagine when doing a provisional BER off the plans they are asked questions about how to meet the regs with minimal hassle etc.

Many assessors wouldn't put much thought into it and just give you the quickest answer that will improve the rating without considering the wider picture.

As part of my degree we did a module in BER and needed to carry out a provisional BER on a set of plans.

To do it to the standard I thought was almost 100% correct most of the class must of put about 12 hours work into it (This was our 1st BER)

Now I know you would speed up with practice but at the rock bottom rates some are charging there is no way they could do even 5 or 6 hours work never mind 12 .

BryanF

timmy4u2 wrote: »

Why are BER assessors giving advice?

Outkast_IRE wrote: »

Because as part of doing a BER they need to recommend ways to improve the the BER score you got. Its part of the report they must do for every house.

And I would imagine when doing a provisional BER off the plans they are asked questions about how to meet the regs with minimal hassle etc.

It doesn't really require much thought.

As part of my degree we did a module in BER and needed to carry out a provisional BER on a set of plans.

I'm not clear on where in the BER advisory note, dry-lining is offered as an option on a new build ( ill take advice on this?)

its interesting that you did this as part of a degree, but you state it doesn't really require much thought?

But Just to go back to the OP

HoofRocks wrote: »

Recently had our BER done. He suggested we use board insulation in the cavity and internal insulation on the walls. ... I've went back with this and he is going to look at this option however he said his concerns are how to prevent cold bridging if we do not have internal insulation.
.

perhaps if the assessor had done a degree in a building related topic he would understand the principles of thermal bridging and read around the topic

perhaps the OP should refer his BER assessor to:
BS EN ISO 13370_2007 thermal performance

Outkast_IRE

BryanF wrote: »

its interesting that you did this as part of a degree, but you state it doesn't really require much thought?

I wrote that in an unclear way apologies. I may edit it.

To expand on what I meant to say was that some of the BER assessors that are doing this type of work, aren't knowledgeable enough or don't care enough to give good advice, so they don't put much thought into their report, and if asked questions will give the easiest answers such as internally insulate to improve etc without considering the effect this may have on the building or if its a suitable solution, they merely care what effect it has on their figures in the DEAP software.


Its an elective that I chose this year as part of my degree (Building Services Eng ). My degree leads onto an Hon Degree in Building Energy Systems and we can choose a module about Commercial BER as part of that. Its a pretty good approach as it gives interested students a more rounded view of energy usage. Plus I have an interest in the area myself.

We don't get enough hours to become registered but it gives us a good understanding of the software and how to carry them out and recommend improvements etc.