What is Thermal Modelling?

With the latest publication of Technical Guidance Document to Part L of the Irish building regulations, it is clear that the elemental thermal performance (U-values) of the building envelope has been further improved in order to limit the primary energy use and reduce CO2 emissions for both new builds and improvements to existing dwellings.

In conjunction with increased insulation levels in the fabric of buildings, heat losses due to thermal bridging have become increasingly important. This in turn has increased the demand for such thermal bridging to be thermally modelled.

As outlined in clause of Technical Guidance Document (TGD) Part L

  • To avoid excessive heat losses and local condensation problems, reasonable care should be taken to ensure continuity of insulation and to limit local thermal bridging, e.g. around windows, doors and other wall openings, at junctions between elements and other locations. Any thermal bridge should not pose a risk of surface or interstitial condensation. Heat loss associated with thermal bridges is taken into account in calculating energy use and CO2 emissions using the DEAP methodology.
  • There are a number of approaches to make reasonable provision with regard to limitation of thermal bridging, this scheme address item (iii) of clause of TGD Part L namely (iii) use certified details which have been assessed in accordance, and comply, with Appendix D, e.g. certified by a third party certification body such as NSAI Agrément or equivalent or certified by a member of an approved thermal modellers scheme or equivalent for all key junctions.

 NSAI Thermal Modellers Scheme: Overview

NSAI Thermal Modellers Scheme: Overview and Documents

NSAI Thermal Modellers Scheme: Overview

The purpose of this scheme is to allow applicants to register as an approved Thermal Modeller of bridging details and junctions, for the purpose of compliance with Clause (iii) of Technical Guidance Document Part L Conservation of Fuel and Energy - Dwellings.

The registration process is twofold:

Applicants must first demonstrate, by way of written submission, that they have a suitable level of competence in order to register as an approved Thermal Modeller.

Applicants must successfully complete 1x3D thermal bridging calculation set by NSAI Agrément and submit 5 sample 2D details as described in section 5. The Applicant will be assessed by the NSAI Agrément and registered as an approved modeller on a web based register. The modeller will be subject to audits (e.g. annual) by the approval body.

NSAI Thermal Modellers Scheme: Documents

Thermal Modeller Application Form

Guidance on application competency & Thermal Modelling validation exercises

NSAI Thermal Modellers Register 

TM Register Number

Name Company Contact Email Certificate of competence


Mark Magennis Xtratherm Ltd


Certificate IAB/TM/01

IAB/TM/02 Andrew Lundberg Passivate Andrew@passivate.ie Certificate IAB/TM/02


Diarmuid Hynes

O'Neill - O'Malley Ltd


Certificate IAB/TM/04


James Walsh

Low Energy Design


Certificate IAB/TM/05


Andrew Dunne

Evolusion Innovation Ltd


Certificate IAB/TM/07


Dara Stewart

IHER Energy Services Ltd


Certificate IAB/TM/08


Patrick Field

O'Connor Sutton Cronin


Certificate IAB/TM/11


Patrice McVeigh

O'Connor Sutton Cronin


Certificate IAB/TM/12


Shane Fenton

Wain Morehead Architects Ltd


Certificate IAB/TM/13


Gary O'Sullivan NSAI


Certificate IAB/TM/14

IAB/TM/15 Robert Ryan Earth Cycle Technologies info@earthcycle.co

Certificate IAB/TM/15

NSAI Thermal Modeller Scheme: Schedule of Fees

Our current fee structure is detailed below and the appropriate fee must accompany your application (inclusive of VAT at 23%).

Travel and expenses are not included and are charged upon completion of the initial audit.

NSAI Approved Thermal Modellers Scheme - Costs

All rates are Excl. VAT at 23%

Initial Registration and Assessment Fee: General Applicants


Initial Registration and Assessment Fee: Graduate of DIT Bolton Street CPD Certificate in Thermal Bridge Assessment (DT775b CPD Cert (TBA))


Re-Assessment Fee or Re-Audit Fee (If required)


Annual Audit/ Registration Fee†


† All registered Thermal Modellers will incur an Annual Audit/ Registration Fee which will fall due on the 1st January on the year following certification.

Contact Scheme Administrator Patricia Walsh