Presentation to the DIT nZEB15 Conference in Dublin, Ireland which explains the methodology to be used in under Irish Building Regulations to assess buildings for surface condensation risk. Some of the Irish government's Acceptable Construction Details (ACDs) are then assessed using this methodology using this methodology. All three of the details assessed fail the surface temperature compliance test of fRsi > 0.75. Guidance from the Minister of the Environment on the assessment of surface condensation risk is examined and also found to be wanting. The unfortunate conclusion of this investigation is that the ACDs cannot be relied upon by designers of buildings to deliver building designs which comply with Irish Building Regulations. Such buildings cannot therefore be certified by Design Certifiers as compliant under S.I.9 of 2014.

1. How to Stop Designing Mouldy Buildings
(and mainstream the thermal bridge)
Simon McGuinness, MRIAI

2. TGD - D.2 Mould growth & surface
condensation
 The key factor used in
assessing the risk of mould
growth or surface
condensation in the vicinity
of thermal bridges is the
temperature factor (fRsi).
 For dwellings, the value of
fRsi should be greater than
or equal to 0.75, so as to
avoid the risk of mould
growth and surface

3. TGD - D.2 Mould growth & surface
condensation
 The key factor used in
assessing the risk of mould
growth or surface
condensation in the vicinity
of thermal bridges is the
temperature factor (fRsi).
 For dwellings, the value of
fRsi should be greater than
or equal to 0.75, so as to
avoid the risk of mould
growth and surface
For fRsi > 0.75
Tsi > 15degC

4. TGD - D.4 Calculation procedures
 The calculation procedure to
establish temperature factor
(fRsi) is outlined in BRE IP
1/06.
 Details should be assessed in
accordance with the methods
described in I.S. EN
ISO:10211.
 Which in turn references I.S.
EN ISO:13788 as
“indispensable for the

5. TGD - D.4 Calculation procedures
 The calculation procedure to
establish temperature factor
(fRsi) is outlined in BRE IP
1/06.
 Details should be assessed in
accordance with the methods
described in I.S. EN
ISO:10211.
 Which in turn references I.S.
hEN ISO:13788 as
“indispensable for the

6. ISO hEN 13788: 2012 (December 2013)
Walls, Floors, Ceilings
fRsi calculation
0.25 m2K/W surface resistance
0.25 m2K/W surface resistance
0.25 m2K/W surface resistance

7. ISO hEN 13788: 2012 (December 2013)
0.10 ^
0.13 >
0.25 ^
0.25 >

8. ISO hEN 13788: 2012 (December 2013)
0.10 ^
0.13 >
0.25 ^
0.25 >

9. Gable/Eaves cavity wall example
ACD 1.09 ACD 1.15

10. Gable/Eaves cavity wall example
ACD 1.09 (Eaves)
and
ACD 1.15 (Gable)
Under construction
In Dublin in 2015

11. Gable/Eaves cavity wall 3D model

12. 3-D Thermal Modelling – Fails fRsi

13. Add 2.5 thermal blocks & mineral wool

14. Thermal Modelling – barely passes fRsi

15. What does the responsible educator do?
 Double-checked the standards
 Revised the syllabus
 Warned previous Thermal Modeller graduates
 Advised the regulators
 Advised the RIAI
 Issued three blog postings on BRegsForum
 Tweeted on social media
 Asked for clarification from the Minister
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16. Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
“I refer to the reply to Question
No. 788 of 15 April 2015 which
addressed the approach to
calculating the temperature
factor in the vicinity of thermal
bridges at junctions and around
openings in accordance with
Appendix D of Technical
Guidance Document L 2011.
….”

17. Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
“I refer to the reply to Question
No. 788 of 15 April 2015 which
addressed the approach to
calculating the temperature
factor in the vicinity of thermal
bridges at junctions and around
openings in accordance with
Appendix D of Technical
Guidance Document L 2011.
….”
Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
”… A surface resistance value
of 0.25 is only used in very
specific situations as outlined in
section 4.4 of the EN ISO
13788 standard which is of
rather limited relevance in this
context and, for that reason, it
has not been referenced at
Appendix D of TGD L 2011 or
referred to in the reply to
Question No. 788 of 15 April
2015.”

18. Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
“I refer to the reply to Question
No. 788 of 15 April 2015 which
addressed the approach to
calculating the temperature
factor in the vicinity of thermal
bridges at junctions and around
openings in accordance with
Appendix D of Technical
Guidance Document L 2011.
….”
Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
”… A surface resistance value
of 0.25 is only used in very
specific situations as outlined in
section 4.4 of the EN ISO
13788 standard which is of
rather limited relevance in this
context and, for that reason, it
has not been referenced at
Appendix D of TGD L 2011 or
referred to in the reply to
Question No. 788 of 15 April
2015.”

19. Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
“I refer to the reply to Question
No. 788 of 15 April 2015 which
addressed the approach to
calculating the temperature
factor in the vicinity of thermal
bridges at junctions and around
openings in accordance with
Appendix D of Technical
Guidance Document L 2011.
….”
Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
”… A surface resistance value
of 0.25 is only used in very
specific situations as outlined in
section 4.4 of the EN ISO
13788 standard which is of
rather limited relevance in this
context and, for that reason, it
has not been referenced at
Appendix D of TGD L 2011 or
referred to in the reply to
Question No. 788 of 15 April
2015.”

20. Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
“I refer to the reply to Question
No. 788 of 15 April 2015 which
addressed the approach to
calculating the temperature
factor in the vicinity of thermal
bridges at junctions and around
openings in accordance with
Appendix D of Technical
Guidance Document L 2011.
….”
Minister of State for the
Environment, Community and
Local Government (Deputy
Paudie Coffey)
”… A surface resistance value
of 0.25 is only used in very
specific situations as outlined in
section 4.4 of the EN ISO
13788 standard which is of
rather limited relevance in this
context and, for that reason, it
has not been referenced at
Appendix D of TGD L 2011 or
referred to in the reply to
Question No. 788 of 15 April
2015.”
?

21. Can the Design Certifier Rely on
the ACDs to deliver a Mould-free
Compliant Design?
On the basis of our work in the last
12 months, it is significantly less
than “certain” that he or she can.

22. Can the Design Certifier Rely on
the ACDs to deliver a Mould-free
Compliant Design?
On the basis of our work in the last
12 months, it is significantly less
than “certain” that he or she can.

23. How did it impact on the DIT nZEB Retrofit
Project 2015?
Current BER: 363 kWh/m2a
Target: 45 kWh/m2a
Saving Per Unit: 318 kWh/m2a
Cabra alone: 3,800 similar houses
Total Savings: 1,208, 400 kWh/m2a
Money Saved: €9million per year
Would fund 200 retrofits per year
In 19 years it would be complete

24. How did it impact on the DIT nZEB Retrofit
Project 2015?
Current BER: 363 kWh/m2a
Target: 45 kWh/m2a
Saving Per Unit: 318 kWh/m2a
Cabra alone: 3,800 similar houses
Total Savings: 1,208, 400 kWh/m2a
Money Saved: €9million per year
Would fund 200 retrofits per year
In 19 years it would be complete

25. Thermal Modelling used to check for fRsi

26. Thermal Modelling used to check for fRsi

27. Thermal Modelling used to check for fRsi

28. How to reduce the cost of retrofit …
€560 per ACD x 178 ACDs x 2 U-values = €100,000
Would take 3 months and employ 5 researchers, or
€10,332 cost per home x 1.3 Million homes = €13,431,600,000

29. How to reduce the cost of retrofit …
€560 per ACD x 178 ACDs x 2 U-values = €100,000
Would take 3 months and employ 5 researchers, or
€10,332 cost per home x 1.3 Million homes = €13,431,600,000
One of these
is “cost
optimal”

30. The Dublin School of Architecture and
Building looks forward to working with
Government and the construction industry to
resolve all the technical issues necessary to
achieve nZEB Retrofit safely, cost effectively
and speedily. By working together, we are
confident we can achieve our national targets.