External wall construction and u-values

2Tractors

Hi,

Long time reader and this forum has given me lots of food for thought, so first off many thanks to the regular and reliable posters. We are at the stage of producing our construction drawings and our architect is looking for a decision on the external walls. As a layman I can't calculate the estimated u-values of our options:
200mm cavity, rigid board insulation & thermally broken wall ties
Or
250mm, pumped bead and s/s wall ties
(or any combination of the above)
Is the architect supposed to provide this detail or is this for the BER assessor? The BER assessor wants to analyse the entire house each time whereas we just want to compare the incremental differences. Is this something we can do ourselves - I'm not afraid of the math but am not sure where to start.

Thanks in advance
2tractors

sydthebeat

Whoever is calculating the compliance of your building specification with part L should be providing this informatIon.

You cannot produce ConstructIon drawings without knowing the spec Complies to regs.

jonniebgood1

Any of the major insulation supply companies will help you with u-value comparisons for different thickness insulations if you want to look on them as separate elements. Sample values should be shown in some of their brochures which can be downloaded as PDF's and they should show values that match your query.

joeirish

sydthebeat wrote: »

Whoever is calculating the compliance of your building specification with part L should be providing this informatIon.

You cannot produce ConstructIon drawings without knowing the spec Complies to regs.

A bit sharp of a response. Perhaps a slightly friendlier tone would be preferable? After all the OP only asked for some friendly advice as far as I can see.

joeirish

2Tractors wrote: »

Hi,

Long time reader and this forum has given me lots of food for thought, so first off many thanks to the regular and reliable posters. We are at the stage of producing our construction drawings and our architect is looking for a decision on the external walls. As a layman I can't calculate the estimated u-values of our options:
200mm cavity, rigid board insulation & thermally broken wall ties
Or
250mm, pumped bead and s/s wall ties
(or any combination of the above)
Is the architect supposed to provide this detail or is this for the BER assessor? The BER assessor wants to analyse the entire house each time whereas we just want to compare the incremental differences. Is this something we can do ourselves - I'm not afraid of the math but am not sure where to start.

Thanks in advance
2tractors

Our architect and engineer have also asked us to decide on the build method and overall BER we are aiming for. Both have said with this information and information about our windows, level of air tightness, heating and ventilation they can suggest specifics. In the meantime I have found that both rigid insulation and bead suppliers/installers have good advice available on websites and information I have Ben sent after inquiring. We have decided that for us bead with 150 mm cavity would give us a good enough u value, about 0.2, but this also depends on the type of bead used. Some seems to give better values than others.

Good luck with the build.

sydthebeat

joeirish wrote: »

A bit sharp of a response. Perhaps a slightly friendlier tone would be preferable? After all the OP only asked for some friendly advice as far as I can see.

The op asked who was supposed to provide the information and i answered correctly.

If you don't understand that that's your problem. Also, when you are made a moderator you can come back to me and comment on the tone of my posts, but until then keep your nose where it belongs.

MicktheMan

sydthebeat wrote: »

Whoever is calculating the compliance of your building specification with part L should be providing this informatIon.

You cannot produce ConstructIon drawings without knowing the spec Complies to regs.

+1

2Tractors

Thanks for the replies. The BER assessor was responsible for ensuring we met part L etc but was reluctant to provide any colour or recommendations and just wanted to do a report on the specs provided. On this basis we found another assessor who is willing to work with us on the design/build rather than just testing the end result.

sydthebeat

2Tractors wrote: »

Thanks for the replies. The BER assessor was responsible for ensuring we met part L etc but was reluctant to provide any colour or recommendations and just wanted to do a report on the specs provided. On this basis we found another assessor who is willing to work with us on the design/build rather than just testing the end result.

Good decision.
There's a huge variance in quality of assessor and its generally a good idea to find one who is also an architect / technician

Carpe Diem

I am interested in teasing out peoples opinions on their preferred wall construction. I am currently in design stage for a dwelling, and I had assummed the following, outside inwards: external plaster; 100mm block; 150mm Cavity Pumped; 100m inner block, and standard skim finish.

Rabbo

Carpe Diem wrote: »

I am interested in teasing out peoples opinions on their preferred wall construction. I am currently in design stage for a dwelling, and I had assummed the following, outside inwards: external plaster; 100mm block; 150mm Cavity Pumped; 100m inner block, and standard skim finish.

Assuming 'silver' bonded bead insulation (lambda 0.033) and normal density blocks, the u value of that construction is approx 0.21. The maximum permitted u value for walls for current regs is 0.21. However the house also has to comply with other overall energy performance coefficients and you will find that meeting the maximum permitted u values will not cut it.You should look at wider cavity or external insulation.
You will need a competent BER assessor (Architect/Engineer/Technician) to look at the entire insulation airtightness and heating strategy of the house with you.





I would ignore the subtle anti-engineer bias from some contributors on this forum. Whether they like it or not, engineers can play an important role in the construction of a house on not just structural issues and will even more so from next month on.

sydthebeat wrote: »

Good decision.
There's a huge variance in quality of assessor and its generally a good idea to find one who is also an architect / technician

gooner99

2Tractors wrote: »

Thanks for the replies. The BER assessor was responsible for ensuring we met part L etc but was reluctant to provide any colour or recommendations and just wanted to do a report on the specs provided. On this basis we found another assessor who is willing to work with us on the design/build rather than just testing the end result.

Hi.What wall/insulation method did you go with in the end?

2Tractors

Hi,

after going through every option and getting mixed advice on every option we went for a 150mm cavity with a full fill board. Like everything it has it's pros & cons.

gooner99

2Tractors wrote: »

Hi,

after going through every option and getting mixed advice on every option we went for a 150mm cavity with a full fill board. Like everything it has it's pros & cons.

Is that the 140mm full fill board you used.Are you in the house,how is it performing?