DHAPT - Domestic House Air Permeability and Pressure Testing

Conservation of fuel and power

Approved Document L1A

Section 2: Quality of construction

and commissioning

49 As required by Regulation 17C, dwellings

should be constructed and equipped so that

performance is consistent with the predicted

DER. As indicated in paragraph 25, a final

calculation of the DER is required to reflect any

changes in performance between design and

construction and to demonstrate that the building

as constructed meets the TER.

The provision of information referred to in

paragraph 27 and Appendix B will assist BCBs

in checking the key features of the design are

included during the construction process.

CRITERION 4 – BUILDING FABRIC

50 In accordance with Part L and Regulation 7,

the building fabric should be constructed to a

reasonable quality of construction so that:

a. the insulation is reasonably continuous over

the whole building envelope; and

b. the air permeability is within reasonable limits.

Continuity of insulation

51 The building fabric should be constructed so

that there are no reasonably avoidable thermal

bridges in the insulation layers caused by gaps

within the various elements, at the joints between

elements, and at the edges of elements such as

those around window and door openings.

52 Reasonable provision would be to:

a. adopt approved design details such as those

set out in the reference in footnote

; or

A list of additional approved details may be

provided in due course.

b. to demonstrate that the specified details

deliver an equivalent level of performance

using the guidance in reference in footnote

53 In addition, the builder would have to

demonstrate that an appropriate system of site

inspection is in place to give confidence that the

construction procedures achieve the required

standards of consistency. For those using the

approved details approach (paragraph 52a))

a way of achieving this would be to produce

a report demonstrating that the construction

checklists included in the reference at footnote

have been completed and show satisfactory results.

It could be helpful to builders and building control

bodies if such reports are signed by a suitably

qualified person.

Air permeability and pressure

testing

54 In order to demonstrate that the specified

air permeability has been achieved, Regulation

20B states:

Pressure testing

20B.–(1) This regulation applies to the erection of

a building in relation to which paragraph L1(a)(i)

of Schedule 1 imposes a requirement.

(2) Where this regulation applies, the person

carrying out the work shall, for the purpose of

ensuring compliance with regulation 17C and

paragraph L1(a)(i) of Schedule 1:

a. ensure that:

i. pressure testing is carried out in such

circumstances as are approved by the

Secretary of State; and

ii. the testing is carried out in accordance

with a procedure approved by the

Secretary of State; and

b. subject to paragraph (5), give notice of the

results of the testing to the local authority.

(3) The notice referred to in paragraph (2)(b) shall:

a. record the results and the data upon which

they are based in a manner approved by the

Secretary of State; and

b. be given to the local authority not later than

seven days after the final test is carried out.

(4) A local authority is authorised to accept, as

evidence that the requirements of paragraph

(2)(a)(ii) have been satisfied, a certificate to that

effect by a person who is registered by the British

Institute of Non-destructive Testing in respect of

pressure testing for the air tightness of buildings.

(5) Where such a certificate contains the

information required by paragraph (3) paragraph

(2)(b) does not apply.

55 The approved procedure for pressure testing

is given in the ATTMA publication ‘Measuring Air

Permeability of Building Envelopes’

. The manner

approved for recording the results and the data

on which they are based is given in section 4 of

that document.

L1A

Information Paper IP01/06 Assessing the effects of thermal bridging at

junctions and around openings in the external elements of buildings,

BRE, 2006.

Measuring Air Permeability of Building Envelopes, ATTMA, 2006.

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