PCMs are materials that store and release large amounts of heat as they change phase from solid to liquid, allowing them to regulate temperature without itself changing in temperature. They effectively store latent heat of phase change within a narrow temperature range. Microencapsulation provides effective packaging of PCMs by creating a huge surface area for heat transfer when incorporated into building materials. This allows PCMs to function as thermal mass to buffer temperature in the comfort range, absorbing and releasing heat more quickly than conventional building materials but over a narrower temperature band. PCMs should be used in conjunction with insulation, shading, orientation and ventilation strategies to effectively control interior temperatures.

1. Introduction to Phase Change
Materials
Phase Energy Ltd
Thermal Comfort Event
10th February 2015

2. What are PCMs?
1kg
0oC
1kg
80oC
334 kJ/kg334 kJ/kg
 PCMs are latent (hidden) heat storage materials i.e.:
 They store or release large amounts of heat as they change phase
(solid liquid)
 They store or release heat without changing temperature
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3. PCMs – “clever” thermal mass
PCMs are thermal mass, NOT insulation!
 Idealised graph
Heat Energy
Latent Heat
Solid
Liquid
Temp.
Tp
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4. Effective packaging
 Microencapsulation provides effective packaging in open porous support
materials
 Huge surface area – good heat transfer
 Building materials with PCMs provide passive thermal comfort
2µm
Polymer shell
Wax
Fp: 23°C
DH: 100kJ/kg1-5µm
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5. How do they work in construction?
 PCMs provide thermal mass
 Unlike concrete, brick etc. they
provide most of their effect over a
narrow temperature range
 Act like lightweight structure
above and below their melt/freeze
temperature range
 Act like a heavyweight structure
around the “comfort range”
 Heat up and cool down quickly
but buffer effectively in the
comfort range 0
50
100
150
200
250
300
40 mm
Concrete (80
kg/m2)
18 mm OSB
(11.7 kg/m2)
12.5 mm
Plasterboard
(11.25 kg/m2)
CoolZone
ceiling tile
(25kg/m2)
89
22 13
31
89
22
13
140
89
22
13
31
16 - 20oC 20 - 24oC 24 - 28oC
Idealised heat storage capacity (Wh/m2)
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6. Heat absorbed vs. temperature
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7. Where to use PCMs?
 For any thermal mass to be effective it should be in contact with room air
Wall construction U-value
W/m2K
Admittance
W/m2K
Kappa value
kJ/m2K
Plaster 13 mm
Brick 100 mm
Brick 100 mm
2 4.26 169
Plasterboard 13mm
Mineral wool (quilt) 150
mm
Plaster 13 mm
Brick 100 mm
Brick 100 mm
0.24 0.73 9
Drywall 13 mm
Cavity 10 mm
Aerated block 100 mm
Cavity 150 mm (Mineral
wool)
Brick 100 mm
0.19 1.86 9
Values are estimates based on the Arup/Concrete Centre software
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8. Should they be used by themselves?
 PCMs, like sensible thermal mass, should be used in conjunction with
other temperature control measures e.g.:
 Insulation
 Shading
 Orientation
 Ventilation
Ideally this should be night-time purge ventilation (3 – 5 ach) not
just MVHR (0.3 - 0.5 ach)
The heat stored in the thermal mass should be released overnight
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