| CASE
STUDY |
Low Energy
Whole House Refurbishment |
CHALLENGE
In early 2009 Knauf Insulation undertook a project to internally
insulate an 1890’s Victorian mid terrace property to current energy
standards. The aim was to install systems that could be undertaken
by any competent builder to achieve an effective and efficient low
energy refurbishment at a modest marginal cost over a normal
refurbishment. The attractive brick frontage made the property less
suitable for external wall insulation (EWI) but ideal for Knauf
Insulation’s Internal Wall Insulation (IWI) system using their
patented EcoStud as a replacement for the more traditional timber
stud framing. To provide a side by side comparison, a Knauf
Insulation insulated metal stud system was also installed in part
of the property.
This private rental property had been damaged by a tenant and
required renovation. Knauf Insulation assisted the landlord and his
builder to enable a ‘whole house - low energy’, refurbishment to be
undertaken with an emphasis on a low marginal cost.
Survey Summary:
| Element |
Observation |
Comment |
| Walls - solid |
No insulation |
Very poor |
| Floor |
No insulation |
Poor |
| Loft |
100mm |
Inadequate |
| Boiler |
New condensing |
Very good |
| Heating controls |
TRV’s |
Good |
| Windows |
Double glazed |
Adequate |
| Doors |
UPVC |
Adequate |
| Lighting |
Incandescent |
Very poor |
INTERNAL WALL INSULATION
 |
 |
 |
 |
| Figure 1 |
Figure 2 |
Figure 3 |
Figure
4 |
Figure 1 shows Stage 1 with all fixtures removed and the plaster
removed back to the original 225mm thick brickwork, although in
most cases the EcoStuds would be affixed through the existing
plasterwork.
Figure 2 shows Stage 2 with the new EcoStud mechanically fixed
to the brick wall and 75mm of EcoBatt friction fitted between to
ensure a complete coverage of insulation across the whole wall.
Figures 3 and 6 show Stage 3 with the 12.5mm vapour check
plasterboard fixed to the EcoStud framework in the bathroom and the
living room. The overall reduction in floor area was less than 2
per cent.
 |
 |
| Figure 5 |
Figure 6 |
THE SYSTEM (figure 4)
- EcoStud which has an overall size of 50mm wide
x 75mm deep x 2400mm long to replace a typical size of timber stud.
This comprises Polyfoam extruded polystyrene laminated to Oriented
Strand Board (OSB). EcoStuds were mechanically fixed to the wall
with the OSB facing into the room using 130mm screws and plugs, a
minimum 40mm fixing penetration into the wall is required.
- 75mm thick EcoBatt water repellent glass
mineral wool slab with a thermal conductivity of 0.032 W/mK
friction fitted between the EcoStuds to ensure intimate contact
between the inside of the wall and the back of the plasterboard
thereby preventing unwanted air movement and draughts through the
system.
- 27mm Polyfoam Linerboard, a laminate of 17.5mm
Polyfoam extruded polystyrene and 9.5mm Knauf plasterboard fitted
around all window and door reveals to limit cold bridging and
surface condensation. 27mm Polyfoam Linerboard was also installed
at all party wall junctions to a minimum width of 400mm and the
full height of the rooms in order to prevent heat loss and the
potential for condensation and mould growth in internal
corners.
- 12.5mm vapour check plasterboard attached to
the OSB of the EcoStuds using 25mm drywall screws with all edges
sealed with Knauf Multi Purpose Sealant to prevent air movement
behind the wall lining reducing the thermal performance of the
installed system. Knauf Insulation also used the alternative Knauf
metal framing system at the front of the property to assess
suitability and timing of the two installations.
|
|
Mid-terraced house,
Doncaster
A low cost ‘whole house’ low energy refurbishment - 1890’s
Victorian mid terrace to current energy standards.
Using the standard trade skills held by a general builder this
was a ‘whole house low energy’ refurbishment at a modest marginal
cost compared with ‘business as usual’.
An attractive brick frontage made this property ideal for Knauf
Insulation’s innovative glasswool internal insulation systems
coupled with suspended wooden floor / loft insulation and low
energy lights.
The reduction in floor area was less than 2% and an estimated
£2,800 was added to the renovation costs (excluding one off
training and instrumentation).
Even though the property already had ‘better than average’
energy efficiency, the low energy upgrade delivered:
- Reduced CO2 emissions by 1.80T per year
- Reduction of 52% in CO2 emissions, excluding
appliances
- SAP rating increased from 63D to 82B
- Energy savings of approx £400pa
- Increased resilience to fuel price rises
- Improved comfort
Better still, it is readily replicable across millions of
similar homes across the UK.
|
Both the Knauf Insulation IWI system and metal system resulted
in an improvement of the U-value from approximately 2.00
W/m2K to 0.35 W/m2K, an improvement in thermal
performance of almost 80 per cent.
At Doncaster there was little time difference between the
installations of both systems, but the Knauf Insulation IWI System
proved a more cost effective way to achieve the same level of
thermal performance. In total the builder installed 73m2
of internal wall insulation into the property.
Figure 5 shows the existing 100mm thickness of insulation
between the ceiling joists, topped up with a second layer of 200mm
Loft Roll.
INTERMEDIATE FLOOR
Insulation was also fitted between the timber floor joists and
the external wall to ensure continuity of insulation between the
two levels. This eliminates any major thermal bridge through the
insulated internal dry lining system.
SUSPENDED TIMBER GROUND FLOOR
The front of the property had a ¾ height cellar above which was
the timber floor of the living room. Knauf Insulation took the
opportunity of insulating this area from below with 150mm of glass
mineral wool friction fitted between the timber floor joists. As
the cellar was prone to seasonal flooding, with a high moisture
content in the cellar atmosphere, it was decided to use EcoBatt
water repellent slab in 2 layers of 75mm to fully fill the 150mm
deep floor joists and ensure the insulation was in close intimate
contact with the underside of the timber floor boards to eliminate
air movement. Figure 7 below shows part of the cellar ceiling.
A new tightly fitting UPVC door was fitted at the top of the
cellar stairs to prevent cold air from entering the kitchen area,
and as the internal wall to the dining room abutted the cellar
atmosphere, it was also insulated with the Knauf Insulation IWI
System. At the same time the underside of the staircase to the
first floor was battened out and insulated.
 |
 |
| Figure 7 |
Figure 8 |
SYSTEM MONITORING
In conjunction with University College London, Knauf Insulation
have also installed monitoring equipment to enable measuring of the
conditions Figure 5 at the interface of the insulation and internal
face of the solid wall. Permanent in-situ sensors have been
installed in each room to measure relative humidity and temperature
and this data is collected in a logger located in the cellar.
University College London will work with Knauf Insulation over
coming years to measure and interpret the results generated.
Sensors were also positioned within the suspended timber ground
floor zone and on the cellar wall.
HoBo type sensors were used in each room to measure the internal
conditions as well as installing an external HoBo sensor to monitor
weather conditions. Figure 8 below shows the set up of the data
logger.
The new tenant has agreed to maintain a daily activity log of
the use of washing machines etc to inform the project team when
high levels of moisture vapour are being generated.
ENERGY PERFORMANCE IMPROVEMENT
The Energy Performance of the property prior to the low energy
refurbishment (which had a condensing boiler with radiators in each
room, UPVC windows and doors and 100mm of glass mineral wool loft
insulation) was SAP 63D with a CO2 emission rate of 3.80 tonnes per
annum, excluding appliances. The property after the low energy
refurbishment achieved a SAP 82B with a CO2 emission rate of 1.80
tonnes per annum, a 52 per cent reduction in CO2
emissions. The calculated energy savings are approximately £300 per
annum, however, based on current fuel costs a figure of £400 would
be more appropriate, with greatly improved comfort conditions.
| Element |
U-values before Treatment (W/m2K)
|
U-values after Treatment (W/m2K)
|
| Walls |
2 |
0.35 |
| Roof |
0.43 |
0.13 |
| Floor |
0.71 |
0.21 |
COST BREAKDOWN
The Knauf Insulation IWI System is a highly cost-effective
system for upgrading existing properties to current Building
Regulation thermal standards and beyond. The marginal cost of
installing the Knauf Insulation IWI System, over and above the work
that was required to bring the property up to a decent standard,
was approximately £2800. The reduction in energy bills results in
the marginal installation costs being re-couped after approximately
7 years based on current energy prices.
