20Dec11
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Insulating A Granite House Having Original Cornice
Be proactive. It is expensive to be inactive.
The Result
The attic and lay-ins were insulated with 10cm mineral wool in 2003. The mineral wool was
placed under the floorboard. Costs of materials were £120. The energy savings were 20,000kWh
per year.
From 2003 to 2011 the total savings were £4800.
In 2011, 75% of the walls were insulated. The energy savings are 19000kWh per year. Costs of
materials are £608.
http://www.fahrenergy.org.uk/install/EnergyBillIncrease2003To2011.pdf
Brief Construction Introduction
A typical Aberdeen granite house is build of 35cm thick granite walls. A number of wood sticks
are fixed in the cracks between the stones. 3cm thick beams of wood are attached to the wood
sticks. The wall plates are nailed onto the beams. This leaves a 3cm space (cavity) through
which fresh air flows to avoid moisture and rot.
The air, which flows through the wall cavity, arrives from the crawl space under the house. A
number of vents in the foundation supplies the crawl space with air, especially when the wind
blows.
Wall cavity
Wall
Insulation Value
The insulation quality of a granite wall is composed of the 35cm thick granite wall plus the
gypsum or cement wall.
Granite has a very poor insulation value. Due to the necessary airflow in the wall cavity, the
temperature of the wall tends to follow the outside air temperature.
As granite has a large heat storage capacity, temperature changes of the wall are dampened by
the near proximity of the granite.
The combination of these two opposite effects of the wall temperature emanates as follows:
• On calm days the cavity airflow is very low and the storage effect of the granite ‘wins’.
Outside temperature and sunshine takes long time to change the wall temperature. Cold
nights have moderate effect.
• On stormy days the outside temperature ‘wins’. The wall temperature tends to follow the
outside temperature.
Insulating A Granite House With Cornish.doc
Copyright FAHRenergy Ltd 2011 - 2012
20Dec11
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Wall Insulation
Introduction
1. The texture of the granite wall is the ‘look’ of the house. No cost effective changes can take
place here. The wall has to be insulated on the inside.
2. Cornice on the wall are expensive or impossible to move.
The solution
Walls marked
have
been insulated in the space
between the lay-in and the
roof (10cm mineral wool).
have
Walls marked
been insulated on the inside
wall (5cm Kingspan). This
has increased the wall
thickness.
The cornice has been
extended to accommodate
the new wall.
The result: To any unaided eye the extended cornice looks original.
The illusion has been reached by profiling a kiln dried timber 18mm*94mm*2100mm.
The profile:
The profile (cornice addition) fits into the existing cornice:
Cornice
Profile
Insulation
Insulating A Granite House With Cornish.doc
Copyright FAHRenergy Ltd 2011 - 2012
20Dec11
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The 5cm thick Kingspan polyurethane insulation had one side cut at 56 degrees and glued to the
wall 12mm beneath the cornice. The 12mm gives space for
the cornice addition.
To prevent the insulation from
sliding down the wall while the
glue was curing, a couple of
90mm screws and discs were
used on each plate.
The ring shows the 12mm
space and the 56 degree cut out
of the insulation.
At the floor level the skirting boards were removed.
Wallpaper was glued on
top of the insulation and
painted.
New skirting boards were
fitted.
The result may be seen on
the picture to the right.
Electrical Sockets
The skirting boards around the old sockets were left. A new socket was fitted with a plug and
connected to the old socket.
Pictures On The Wall
The Kingspan insulation panels are sufficiently hard to function as a wall surface but too soft to
hang any subject onto. Due to this we decided to insert wooden bars onto which various items
may be hanged.
Adding gypsum plates to the wall was thus unnecessary.
The Insulated Rooms
The house has two lounges, 4 rooms, two toilets, one kitchen and a conservatory.
Insulating A Granite House With Cornish.doc
Copyright FAHRenergy Ltd 2011 - 2012
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Room One
The Fresh Air Heat
Recovery Ventilator
(HRV) inlet and outlet
are marked with a
circle.
The FAHRenergy
HRV is placed in the
attic (loft).
Room Two
Room Three
Toilet One
Old air out to HRV is positioned
above the toilet (see circle)
Insulating A Granite House With Cornish.doc
Copyright FAHRenergy Ltd 2011 - 2012
20Dec11
www.fahrenergy.co.uk
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Fresh Air With HRV Improves health And Saves Money
There is no longer a reason to languish in old stale mouldy air
Fresh Air And Health
Fresh air in our homes becomes more and more important as we stay longer inside and improve
our houses against heat loss.
FAHRenergy HRV Saves Money
FAHRenergy’s unique Heat Recovery Ventilators and concept allows for fresh air at no running
cost. Indeed it saves money.
More about the savings in this link:
http://www.fahrenergy.org.uk/install/FreshAir.pdf
Insulating A Granite House With Cornish.doc
Copyright FAHRenergy Ltd 2011 - 2012