The document discusses internal wall insulation (IWI) options for older buildings in England. It summarizes a KTP project that tested 8 different IWI systems, including 4 breathable and 4 conventional systems. Monitoring and modeling showed that breathable insulation allowed walls to dry out faster by up to 22% compared to 8% for non-breathable insulation. The project aims to find a safe, effective solution for mainstream IWI application in typical 9-13" brick buildings, focusing on hygrothermal performance and moisture transport. More evidence is still needed regarding long-term performance and faults to ensure solutions are both safe and practical.

1. Internal Wall
Insulation
Valentina Marincioni – KTP associate

2. More than 4.6m pre-1919 dwellings
in England only

3. Why Internal Wall Insulation (IWI)?
Conservation areas Traditional buildings
Listed buildings Decorative façades
COST

4. But…
Energy loss through external wall in %
Thickness of internal insulation in cm External
insulation

5. But…
5

6. And..
Existing wall exposed to low temperatures
Increase of RH risk of mould growth and
timber decay

7. KTP project
To find a safe, effective, saleable solution for
mainstream application.  focus on 9” to 13” brick
buildings in England.
Three legged strategy:
• Modelling
• Laboratory testing
• Case studies, real life monitoring

8. KTP project Test Methodology
• Monitoring interstitial condensation by
measuring the RH at the wall-insulation interface
• Comparison of monitoring and
hygrothermal modelling
(WUFI Pro)
• Comparative testing of
breathable and non-breathable systems

9. KTP project Test Methodology

10. KTP project Test Methodology
• 8 different internal insulation
systems
• 4 breathable systems (wood
fibre) from NBT– development
of two new systems
• 4 conventional systems – the
most common IWI systems in
the UK market

11. Transport mechanisms
• Vapour diffusion
• Liquid transport
• Moisture convection
(through leaks)

12. Moisture sources
• Wind driven rain
• Internal water vapour
(vapour production, low ventilation..)
• Construction moisture
• External water vapour
(solar radiation..)

13. Conventional VS Breathable Insulation

14. Moisture content Location
35
30 Swansea, SW
Moisture content [M-%]
25 Liverpool, SW
20
Manchester, SW
15
London, SW
10
40 60 80 100
Insulation Thickness [mm]
Pavadentro on 9” solid brick, 1%DR

15. Moisture content Orientation
35
30
Swansea, SW
Moisture content [M-%]
25
20
15
Swansea, N
10
40 60 80 100
Insulation Thickness [mm]
Pavadentro on 9” solid brick, 1%DR

16. Moisture content Orientation
35
30
Moisture content [M-%]
25
20
15 London, N
London, SW
10
40 60 80 100
Insulation Thickness [mm]
Pavadentro on 9” solid brick, 1%DR

17. Moisture content Vapour Control Layer
35
33
sd-value [m]
31
0
Moisture content [M-%]
29
27 5
25
100
23
21
19
17
15
London-N London-W Swansea-N Swansea-W
100mm Pavaflex on 9”solid brick, 0 DR

18. Moisture content Impact of density
35
30
100mm Pavaflex
Moisture Content (M-%)
Ρflex = 53 kg/m3
25
20 100mm Pavadentro
Ρdentro = 175 kg/m3
15
10 20mm Pavaclay &
80mm Pavaflex
5 Ρclay = 380 kg/m3
Ρflex = 53 kg/m3
0
0-10mm 10-20mm 20-30mm 30-100mm
Depth in construction
On 9”solid brick Swansea 1% DR

19. KTP project Test Methodology
Test 1
Δ VP
• Only vapour is considered
ΔVP
ΔVP
• Wall exposed to:
• Winter climate (Nov, Dec)
• Spring climate (May, June)

20. KTP Comparison of monitoring and modelling
RH - simulated
RH - monitored
Dry-fit Pavadentro
Wetting well simulated – drying underestimated

21. KTP Comparison of monitoring and modelling
RH - simulated
RH - monitored
Pavaclay and Pavaflex

22. KTP Comparison of monitoring and modelling
RH - simulated
RH - monitored
PIR

23. KTP Comparison of monitoring and modelling
• WUFI calculations agree with the measured data
during winter
• The simulation underestimates the dry-out
potential of the materials

24. Drying: -400 VPX
Breathable materials: 22% average RH reduction
Non-breathable materials: 8% average RH reduction

25. Drying: 0 VPX (typical spring conditions)
Breathable materials: 6.5% average RH reduction
Non-breathable materials: 1% average RH reduction
Higher speed of desorption in breathable materials

26. Higher speed of desorption in breathable materials
• Low vapour permeability (vapour
movement on both sides)
• Capillary suction: moisture is wicked
away from the critical interface
• Hygroscopicity: breathable materials
can store moisture

27. KTP Other tests
• In-situ U-value measurements with heat flux plates
• Blower-door test
• Joist-end moisture content
• IR thermography

28. Way forward for IWI on solid walls?
• Must take into account faults and failures both
short and long term
• Need useful safe and buildable solutions,
not over-optimised solutions
• Pointless and dangerous going for too low U-values
• Need much more evidence, as well as proper data
sets for materials and weather
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