Thermal Performance of Traditional Masonry Walls - Historic Scotland

In situ U-value measurements
in traditional buildings –
preliminary results.
Paul Baker
Centre for Research on Indoor Climate & Health
Glasgow Caledonian University
Paul.Baker@gcal.ac.uk

The Project
‣ The main objective of the study was to assess the actual thermal
performance of traditional building envelopes, to provide guidance
for energy performance assessments and implementing energy
efficiency measures in such buildings.
‣ In situ U-value measurements of walls were made on behalf of
Historic Scotland between November 2007 and April 2008 in a
sample of buildings representing traditional masonry construction n in
Scotland.
‣ Measurements were made of the heat flow directly through each
wall using heat flux sensors mounted on internal surfaces.
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Measurement technique
External Temperature
Room Temperature
Wall Surface Temperature
Interior Surface Temperature
Heat Flux
Meter
3

Heat Flux Sensor
4

External Temperature
Air
Surface
6

Monitoring Period
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The Buildings
‣ Victorian Villa Glasgow
‣ Crichton campus
‣ Lauriston Place Edinburgh
‣ Castle Fraser out-buildings & apartment
‣ Cottage Borders
‣ + Locharbriggs sandstone test wall
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Location Stone Type Wall thickness Outside
Face
Victorian Villa, Glasgow
Bedroom N-W
Crichton Campus
Blond
Sandstone
600mm Rubble Lath
Ground floor South Locharbriggs 600mm Ashlar Lath
Ground Floor North Locharbriggs 600mm Ashlar Lath
First floor South Locharbriggs 600mm Ashlar Lath
First floor North Locharbriggs 600mm Ashlar Lath
Second floor South Locharbriggs 600mm Ashlar Lath
Second floor North Locharbriggs 600mm Ashlar Lath
Lauriston Place, Edinburgh
Ground floor front Craigleith 600mm Ashlar Lath
elevation
Basement front wall Craigleith 600mm Ashlar Hard
Inside Face
Basement rear wall Craigleith 600mm Cement Plasterboard
No 28 Rear wall 1 st floor Craigleith 600mm Rubble Plasterboard
Front wall, below
window
Craigleith 300mm Ashlar Hard
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Location Stone Type Wall thickness Outside
Face
Castle Fraser
1 st floor bedroom Kemnay Granite 600mm Rubble Lath
Ground floor turret Kemnay Granite 350mm Rubble Hard
Inside Face
Ground floor stable Kemnay Granite 400mm Rubble Plasterboard
office
Gardner’s Bothy Kemnay Granite 400mm Rubble Lath
Weens Cottage, Borders
Ground floor, East Red Sandstone 400mm Rubble Hard
elevation
North gable, ground Red Sandstone 400mm Rubble Hard
floor
West wall Brick 400mm Rubble Hard
Bathroom wall, West
elevation
Red Sandstone 400mm Rubble Hard
10

Snuffmill Road, Cathcart, Glasgow
0.8W/m
2 K
Lath & Plaster
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Crichton Campus
U-values W/m 2 K
South
North
Second 0.6 0.8
floor
First floor 1.5 1.0
Ground
floor
1.0 1.4
Ventilated Walls!!!!!
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Lauriston Place, Edinburgh
Ground Floor Front
Elevation 1.4W/m
W/m 2 K
Under Window
2.4W/m
W/m 2 K
Lath & plaster
hard
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Lauriston Place
Basement Rear Wall 1.0W/m 2 K
hard
plasterboard
Basement Front Wall 1.5W/m 2 K
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Lauriston Place Basement Floor
Concrete Only 3.5
Concrete + Spacetherm 0.6
3.5W/m
2 K
0.6W/m
2 K
15

Castle Fraser Apartments
0.8W/m
2 K
Lath & Plaster
16

Castle Fraser Bothy
0.9W/m
2 K
Lath & Plaster
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Castle Fraser Stables
0.9W/m
2 K
Plasterboard
18

Castle Fraser Stables
1.8W/m
2 K
Hard Plastered
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Weens Cottage, Borders
Front Elevation
1.2W/m
2 K
hard
20

Weens Cottage, Rear Elevation
1.1W/m
2 K
hard
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Weens Cottage
Kitchen Extension
1.4W/m
2 K
Side Elevation
1.1W/m
W/m 2 K
hard
hard
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Lab. Test Wall
• 550mm Locharbriggs
Sandstone
• Heat flux meter mounted on
interior rubble finish
• U-value of solid wall estimated =
1.4 W/m 2 K
• Plasterboard mounted on timber
studs fixed to wall interior
• 2 nd heat flux meter mounted on
face of plasterboard
• U-value of wall with
plasterboard = 1.1 W/m 2 K
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Analysis – interior finish
2.5
2
U-value [W/m2K]
1.5
1
Average &
standard devaition
0.5
0
Hard Lath Plasterboard
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Stone type/interior finish
Walls Plastered on the Hard
2.5
U-value [W/m 2 K]
2
1.5
1
0.5
600mm
400mm
350mm
300mm
0
Brick Craigleith Kemnay Granite Red Sandstone
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Stone type/interior finish
600mm Walls with Lath & Plaster
U-value [W/m 2 K]
1.6
1.4
1.2
1
0.8
0.6
0.4
0.2
0
Blond
Sandstone
Craigleith Kemnay Granite Locharbriggs
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Stone type/interior finish
600mm Walls with Plasterboard
1.2
1
U-value [W/m 2 K]
0.8
0.6
0.4
0.2
0
Craigleith
Kemnay Granite
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Analysis
‣ Given small sample size:
• For the walls plastered on the hard there is some correlation
between wall thickness and U-valueU
• The walls with lath and plasterboard finishes have lower U-U
values than those plastered on the hard
• It is not possible to distinguish between the different masonry
types
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Analysis
‣ In the case of the Crichton Campus building (Locharbriggs
sandstone), the six measurements show a greater range than those
made in the other buildings with lath and plaster finishes.
‣ However, the ventilated walls in the Crichton Campus building have
some influence on the U-value U
estimates, particularly on the top
floor of the building.
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Conclusions
‣ The in situ U-values of twenty walls have been carried out covering
part of the range of traditional Scottish masonry constructions and
internal finishes.
‣ Given the sample size it is not possible to differentiate between
different masonry materials.
‣ For walls plastered on the hard, increasing wall thickness improves
the U-value. U
‣ Walls with lath and plasterboard finishes have lower U-values U
than
those plastered on the hard. This demonstrates the insulating effect
fect
of an air cavity.
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Conclusions
‣ Thus far, indicative U-values U
for 600mm masonry walls
are as follows:
• Wall plastered on the hard: 1.5 ±0.4 W/m 2 K
• Wall with lath and plaster: 1.0 ±0.3 W/m 2 K
• Wall with plasterboard: 0.9 ±0.1 W/m 2 K
‣ U-values less than expected given thermal conductivity
of stone (~2 W/mK). Need to consider mortar (thermal
conductivity ~0.7 W/mK) + voids in calculations.
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Further investigations
‣ Further in situ measurement will be carried out during winter
2008/09, with the aims of extending the geographical range of
masonry types within Scotland and also measuring the U-values U
of
floors and roofs.
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