Thermal Regulations - Scotland
Domestic Technical Handbook - Section 6: Energy
The EPBD requires a calculation method that adopts a whole
building approach to energy performance. A new 2005 version of SAP
has been developed that meets this requirement. The SAP worksheet
and specification can be downloaded from www.bre.co.uk/sap2005 In
addition, there is greater emphasis on ensuring that the building
construction meets the standards assumed at the design stage and
that the heating and hot water systems are correctly
commissioned.
How to comply
The four criteria set out below describe the process the
designer and builder must go through to show compliance. SAP 2005
is used to calculate a Target Emission Rate (TER) for a ‘notional
dwelling’ of exactly the same size and shape as the proposed
dwelling and assuming a fixed package of measures as set out in
Table 9. The steps to achieve compliance are set out below.
1. Calculating the CO2 emissions for the proposed
building
The calculated rate of carbon dioxide emissions from the
dwelling (the Dwelling Emission Rate DER) should not be greater
than the Target Emission Rate (TER).
How to comply
Using the Standard Assessment Procedure (SAP 2005), the
CO2 emission rate is calculated for a notional dwelling
of the same size and shape as the proposed dwelling using a fixed
set of criteria for the fabric heat loss, building services and
fuel choice. Tables 2 and 3 lists the criteria used to calculate
the CO2 emission rate. BRE approved SAP 2005 software
incorporates a function that with Scotland selected, automatically
generates the target CO2 emissions level when the fuel
type is selected and the ‘notional dwelling’ dimensions and 'living
area fraction' have been input into the programme.
To calculate the Dwelling Emission Rate (DER), the SAP
calculation is repeated, but this time inserting the proposed
U-values, building services and low or zero carbon energy sources
for the proposed building. If the DER of the proposed building is
less than or equal to the TER, Standard 6.1 has been achieved.
As an alternative to the SAP calculation method, clause 6.16
allows a simplified approach, which is to adopt one of the six
packages of measures listed in Table 9.
Note that a SAP calculation will still need to be done to
produce the information for the Energy Performance Certificate that
must be affixed to every new dwelling – see step 4.
2. Design ‘back stops’
Show that the thermal performance of the building fabric and the
heating, hot water and lighting systems are within the design
limits in the Technical Handbook.
How to comply
Standards 6.2 to 6.8 in the Technical Handbook mainly recommend
‘back stop’ levels of performance, which in most cases will need to
be exceeded in order to meet the level of energy efficiency
required in Standard 6.1 of the Handbook.
These back stops include:
- limiting U-values (see Table 4)
- levels of air permeability
- heating and hot water systems and controls
- insulation of pipes, ducts and vessels
- artificial lighting
- mechanical ventilation and air conditioning
Table 4 - Limiting U-values
(W/M2K)
|
Individual Element
|
(a) Area-weighted dwelling
average
|
(b) Worst sub-element
|
| Wall |
0.30 |
0.70 |
| Floor |
0.25 |
0.70 |
| Roof |
0.20 |
0.35 |
| Glazed openings & doors |
2.20 |
3.30 |
3. Written information
Provide operating and maintenance instructions to enable the
building and its services to be operated in an energy efficient
manner.
How to comply
The owner of the building should be provided with a set of
simple operating and maintenance instructions explaining how to use
the installed heating and hot water system to achieve economy in
use.
4. Energy
Performance Certificate
Every new dwelling should have an Energy Performance Certificate
affixed to it. The Technical Handbook lists out all the information
that should be included on the Certificate. It should be
permanently affixed to the dwelling, in a meter cupboard for
example.
Table 9: Measures to calculate
target carbon dioxide emissions for the 'notional
dwelling'
|
Element or system
|
Gas
(package 1)
|
LPG
(package 2)
|
Oil
(package 3)
|
Electricity
(package 4)
|
Biomass 1
(package 5)
|
Solid fuel
(package 6)
|
| Walls |
U=0.25 |
U=0.25 |
U=0.25 |
U=0.25 |
U=0.25 |
U=0.20 |
| Roofs |
U=0.22 |
U=0.22 |
U=0.22 |
U=0.22 |
U=0.22 |
U=0.20 |
| Floors |
U=0.16 |
U=0.16 |
U=0.16 |
U=0.16 |
U=0.16 |
U=0.16 |
| Openings 2 |
U=0.18 |
U=0.18 |
U=0.17 |
U=0.18 |
U=0.18 |
U=1.50 |
| Allowance for thermal bridging |
0.08 x total exposed surface area3 |
0.08 x total exposed surface area |
0.08 x total exposed surface area |
0.08 x total exposed surface area |
0.08 x total exposed surface area |
0.06 x total exposed surface area |
| Open flues |
none |
one |
one |
none |
one |
one |
| Heating system (pump in heated space) |
Gas boiler roomsealed fan flued 90% efficiency |
LPG boiler roomsealed fan flued 90% efficiency |
Oil boiler roomsealed fan flued 93% efficiency |
Air to water heat pump |
Wood pellet boiler HETAS approved |
Anthracite bolier autofeed in heated space HETAS approved |
| Heating system controls |
Programmer
+ room thermostat
|
Programmer
+ room thermostat
+ TRVs
+ Boiler interlock
|
Programmer
+ room thermostat
+ TRVs
+ Boiler interlock
+ weather
|
Programmer
+ room thermostat
+ TRVs
+ Boiler interlock
|
Programmer
+ room thermostat
|
Programmer
+ room thermostat
+ TRVs
|
| Hot water (HW) system (not applicable if combi boiler) |
Stored HW (from boiler) separate time control for space and
water heating |
Stored HW (from boiler) separate time control for space and
water heating |
Stored HW (from boiler) separate time control for space and
water heating |
Stored HW by electric immersion |
Stored HW (from boiler) separate time control for space and
water heating |
Stored HW by dual electric immersion & solar |
| Secondary space heating |
10% electric |
10% closed wood logburning room heater 4 |
10% closed wood logburning room heater 4 |
10% electric |
10% electric |
10% electric |
| Solar panel evacuated tube-collector efficiency n=0.6,
a1=3 |
none |
none |
none |
none |
none |
4m2 panel between SE and SW, not more that 45degree pitch, no
overshading |
Table 10: The following default
values are used in the 'notional dwelling' for all fuel
types
|
Windows, doors, and rooflights
|
area 25% of total floor area [5]
|
|
Orientation
|
all glazing orientated east/west
|
|
Shading
|
average overshading
|
|
Number of sheltered sides
|
2
|
|
Chimneys
|
none
|
|
Ventilation system
|
natural ventilation with intermittent
extract fans: 4 for dwellings with floor area more than 80
m2, 3 for smaller dwellings
|
|
Air permeability
|
10 m3 /m2h at 50
Pa
|
|
Hot water cylinder (for solar water
heating a combined cylinder with solar store 75 litre, no solar
powered pump)
|
150 litre cylinder insulated with 50
mm of factory applied foam (cylinder in heated space) cylinder
temperature controlled by thermostat
|
|
Primary water heating losses (not
applicable to combi-boiler or immersion)
|
primary pipework insulated
|
|
Low energy light fittings
|
50% of fixed outlets
|
Notes to Tables 9 and 10
1) The biomass column should be used not only where biomass
fuel is to be used but also for biogas, large scale waste
combustion from boilers and waste heat from power stations. It does
not however include dual or multi-fuel which should be taken under
the ‘solid fuel’ column.
2) U is the average U-value of all openings (windows, doors,
rooflights) based on one opaque door 1.85 m2 of U=1.8,
any other doors fully glazed. For windows, doors etc a frame factor
of 0.7, light transmittance 0.80 and solar energy transmittance
0.72 for U greater than or equal to 1.7, 0.63 for U less than 1.7
are assumed.
3) Construction using ‘Accredited Construction Details
(Scotland)’ is considered to correspond to the default figure of
0.08 for thermal bridging (refer clause 6.2.3).
4) Under secondary heating the closed wood logburning room
heater is capable of burning wood only, not multi-fuel.
5) If total exposed façade area is less than 25% of the
floor area, the total exposed façade area.
