Part L

Slates

Does anyone have the new elemental u-values required in the upcoming version of the building regs please

muffler

Link but it mightn't tell you an awful lot

ardara1

Slates wrote: »

Does anyone have the new elemental u-values required in the upcoming version of the building regs please

We're still working on the draft but the Dept of Envir has signed the new Part L into Law on the 24th - but won't let us see it yet!

In the draft document that went to consulation, the AVERAGE U-value allowable were
Walls - 0.27
Floors - 0.25
Roof - 0.22
Windows door - 2.2

These look ok but are average values - take 140mm timber frame with ordinary fibre - no longer permitted - pumped cavities 100mm wide - not permitted.

However in the 9 cases that were used to demonstate compliance
wall were:
For 4 house types - 0.20
For remaing 5 - 0.25

Also floors ranges from 0.20 to 0.22

Roofs from - 0.11 to 0.16

Ops were ALL 1.8

Some had fuel changed from all and in some cases orientation of the building were changed

ALL THIS JUST TO MAKE THE WORK!

But - it was only in DRAFT - what the reality will be remains to be seen! - watch this space. (I have been told 2 different stories - significant changes b from draft - the other clarification not watered down)

smashey

Didn't we have a big thread on this before that just ended up going round in circles?

Mellor

ardara1 wrote: »

In the draft document that went to consulation, the AVERAGE U-value allowable were
Walls - 0.27
Floors - 0.25
Roof - 0.22
Windows door - 2.2

I noticed the inclusion of the "average" in the draft, what does that mean exactly in terms of calculation? At first I thought it was that the total area of the wall has to be under 0.27 (ie wall + opes), but im not sure now.

ardara1

Mellor wrote: »

I noticed the inclusion of the "average" in the draft, what does that mean exactly in terms of calculation? At first I thought it was that the total area of the wall has to be under 0.27 (ie wall + opes), but im not sure now.

Hi Mellor - Average Weighted Average - you can go worse in a particular u-value (to a set max set in the part L document - I think 0.6 for a wall) as long as the rest for the element makes up for it.

Eg. Dormer window wall with 100mm stud just 0.30 - the rest of the walls need to be improved to perhaps 0.25 to make the average allowable 0.27 max

Mellor

Right, makes sense.
So a house built with all elements at the limits, is compliant.
(To that section only of course, might need to be increased to comply with energy usuage etc)

ardara1

Mellor wrote: »

Right, makes sense.
So a house built with all elements at the limits, is compliant.
(To that section only of course, might need to be increased to comply with energy usuage etc)

H Mellor - I haven't found 1 house type that does comply when working to these 'Average' U-values, You must take into account solar gain (orientation) and add in the compulsory 10kWhr/m2 from a renewable source also.

The revision goal is to improve current part l by 40% (I had a conversation with one of the guys that tested the new document - working on a 'rule of thumb' all OPAQUE' elements averaged approx 0.22 in their estimations.

Mellor

Sorry, I was refering to complying with the U-values only, to comply with Part L as a whole you may need to up these. And include other elements such as renewable.

Rule of thumb looks good, .22 is decent min standard, self builders will of course oush this i'd imagine