Monday, April 03, 2006

What the ODPM won’t tell you about the new Part L

Walls — 0.27
Flat ceiling — 0.16
Pitched roof — 0.20
Floor — 0.22
Windows — 1.8
A-rated boiler
Pay close attention to air leakage paths
Be prepared for an air-tightness test but don’t be worried about it

That’s it. Those are the U values and the details you will need to get your new detached house through the new Part L of the England & Wales building regs, which came into play at the beginning of April.

Funnily enough, you won’t find this information in the section of Part L that looks at building new homes, Part L1A. This is because we are meant to be moving to a whole house heat loss approach. This is a fine thing in principle as it recognises that the energy performance of a dwelling is dependent on a variety of factors. The regs suggest that you should have a target carbon emission figure for each house and that it’s up to the designers to figure out how they meet that target. But that doesn’t help designers a great deal because you have to put your designs through a process known as a SAP calculation in order to know what your emission rate is likely to be. You can do this manually via the BRE’s SAP 2005 calculations sheet (warning: it’s six pages and has 120 different steps to go through, many with look-up tables, before you get an answer) or you can do it using software but this is stuff you have to purchase. It’s not the sort of process a house designer is really geared up for: they want to know how much insulation they have to squeeze into the fabric.

But contacts of mine in the insulation business have been busying themselves with the new calculations and are coming up with model designs that will meet the new regs. And that one at the top of this article looks like the dog’s bollocks as regards detached new houses.

Oh, and it looks like bad news for Actis and the multifoil kids. Despite my contact Charlie Duke showing that Actis works pretty well, the powers-that-be are going to require that all insulation meets standard BR443 after 1 Jan 2007. BR443 states that thermal insulation has to have a European Technical Approval to be permissible. That means, in short order, that the insulation has to pass muster with the standard test, the guarded hot box test, which the multifoils don’t do.

7 Comments:

Blogger Les Squires said...

Mark Brinkley gives a pretty good summary of the situation. However, his last point concerning guarded hot box testing of multi-foil insulation materials is not correct. The test is not a "pass-fail" test, it just measures the U-value of the test unit. This is as valid for multi-foils as it is for glass wool or rigid foam board insulation materials. See the Web Dynamics "Thinsulex" web site for more information.

1:14 pm  
Blogger fostertom said...

The confed of multifoil manufs (CMM) has been set up by 4 UK suppliers with the specific aim of getting fully acceptable accreditation "by Christmas" - this includes hammering out test procedures that don't inherently penalise primarily-radiant barriers, which the present 'respectable' test procedures do. The most genned-up supplier's tech guy seems to be Paul Mitton of Euroform (Xfoil) 07748 118841.

11:48 am  
Blogger Les Squires said...

The measurement of multifoil reflective insulation products was the topic of a recent meeting hosted jointly by the BBA & CPA, 19 June 2006. At this meeting, Ray Williams of the National Physical Laboratory explained the design and function of the guarded hot box apparatus, (test method EN ISO 8990). This test method measures the thermal insulation properties of any test structure, taking into account its total conductive, convective and surface emissivity (in effect its I.R. reflective) properties. In other words it fully takes into account “radiant barrier” properties. The guarded hot box test is the only international test method recommended by the Building Regulations Part L (under BR443 Conventions for U-value calculations, issued 2006) and which measures thermal insulation properties of insulation materials as they are installed in a building section.

Some CMM members are claiming thermal insulation values for their products which defy the laws of physics – not generally an indicator of sound scientific work. EN ISO 8990 remains the only recommended test method until such time as EOTA reports on any alternative test.

5:44 pm  
Blogger Les Squires said...

The measurement of multifoil reflective insulation products was the topic of a recent meeting hosted jointly by the BBA & CPA, 19 June 2006. At this meeting, Ray Williams of the National Physical Laboratory explained the design and function of the guarded hot box apparatus, (test method EN ISO 8990). This test method measures the thermal insulation properties of any test structure, taking into account its total conductive, convective and surface emissivity (in effect its I.R. reflective) properties. In other words it fully takes into account “radiant barrier” properties. The guarded hot box test is the only international test method recommended by the Building Regulations Part L (under BR443 Conventions for U-value calculations, issued 2006) and which measures thermal insulation properties of insulation materials as they are installed in a building section.

Some CMM members are claiming thermal insulation values for their products which defy the laws of physics – not generally an indicator of sound scientific work. EN ISO 8990 remains the only recommended test method until such time as EOTA reports on any alternative test.

5:45 pm  
Blogger Les Squires said...

The measurement of multifoil reflective insulation products was the topic of a recent meeting hosted jointly by the BBA & CPA, 19 June 2006. At this meeting, Ray Williams of the National Physical Laboratory explained the design and function of the guarded hot box apparatus, (test method EN ISO 8990). This test method measures the thermal insulation properties of any test structure, taking into account its total conductive, convective and surface emissivity (in effect its I.R. reflective) properties. In other words it fully takes into account “radiant barrier” properties. The guarded hot box test is the only international test method recommended by the Building Regulations Part L (under BR443 Conventions for U-value calculations, issued 2006) and which measures thermal insulation properties of insulation materials as they are installed in a building section.

Some CMM members are claiming thermal insulation values for their products which defy the laws of physics – not generally an indicator of sound scientific work. EN ISO 8990 remains the only recommended test method until such time as EOTA reports on any alternative test.

5:46 pm  
Anonymous Jon said...

Thanks for letting us know what the new regs are.

4:19 pm  
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8:38 pm  

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