Supplementary Commentary to the Submission made on the SEAI Template
RIAI Comments
on the
Public Consultation Document on Dwelling Energy AssessmentProcedure ( DEAP)
12 January 2011
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RIAI Comments
on the
Public Consultation Document on Dwelling Energy Assessment Procedure ( DEAP)
INTRODUCTION
The RIAI welcomes the opportunity to comment on the existing DEAP software initative, taken together with
the DoE/H/LG Draft Part L consultation document, we are highly supportive of the progressive and
committed stance the DoEHLG has taken in making significant improvements in the energy efficiency
requirements of the TGD L.
In particular, the RIAI is supportive of the ‘whole building analysis’ approach and commend the continued
stance of setting overall targets for energy use and carbon emissions in buildings. This is an important
opportunity to enable practitioners to choose the most cost-effective and appropriate design solutions for
each particular dwelling.
1.
General Commentary on Adopted Approach
While acknowledging the ambitious time frame to maximise the energy efficiency of dwellings, there are
substantial limitations to the current approach with the use of DEAP software.
The Irish Construction Industry has begun to embrace more ambitious targets, recognising the reality of zero
carbon in the short term. As such a strong passive house movement has begun adopting principals
developed in Europe, introducing much more sophisticated methodologies of calculating energy
conservation, both in building fabric and services. Examination of the principles of passive house both in
terms of the calculation tools and fabric detailing highlights the limitations of DEAP,
The RIAI proposes that the passive house standard is adopted in the DEAP software considering that the
objective is to achieve a 60% saving, but use of the passive house standards and calculation tools is a more
sustainable approach, as it naturally leads the design of a property towards a zero carbon standard. Instead
the current approach may achieve the 60% saving but will potentially have to be completely abandoned in
favour of totally new approaches to fabric and service design in just 3 years to achieve the zero carbon
targets. Most importantly, in addition, the Passive house approach looks at the property in terms of
maximising solar heat gains as the main heat source of the property which is not possible in DEAP.
2. Main Proposed Amendments
2.1
RIAI Proposed Amendment to MPEPC and MPCPC Methodology.
Observation:
It has been observed in practice, and demonstrated through research, that the MPEPC and MPCPC
methodologies cause vastly varying levels of energy efficiency to be required of different dwellings in
achieving compliance. In particular, it causes a bias against buildings with an efficient form.
Research has shown that this bias is caused by an inconsistency in the methodology used. The RIAI believe
that the situation is unintentional but finds that it is highly unsatisfactory. The RIAI propose an amendment to
allow this unintentional bias to be removed and ensure a fairer system of compliance.
For example, in the research, it was observed that an L-shaped bungalow achieved compliance with an
energy use of 78 kWh/m2/yr, while a mid-floor apartment of the same area and volume had to achieve the
much higher standard of 45 kWh/m2/yr to achieve compliance.
Additionally, because different forms and sizes of dwellings have different energy use targets, as a design
progresses and changes are made, a designer is faced with a constantly shifting energy use target.
It has also come to our attention that there is no policy or regulatory requirement for the MPEPC or MPCPC.
Part L defines DEAP as the tool for demonstrating compliance with the regulation. The regulation does not
mention the MPEPC/MPCPC. DEAP is available for download in two formats, one of which does not contain
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the function to calculate MPEPC. Therefore, it is not always possible to use DEAP to demonstrate
compliance which contradicts the Part L Regulation.
Proposal:
The RIAI propose replacing the MPEPC and MPCPC ratios with a fixed maximum energy use in terms of
kWh/m2/yr and fixed maximum carbon emissions in terms of kgCO2/m2/yr.
Research carried out found that figures of 60kWh/m2/yr and 11.8kgCO2/m2/yr were required to demonstrate
an overall improvement in building standards since 2005.
Outline of the Issue:
In order to make the comparison a ‘reference dwelling’ has been defined in the the guidance to have the
standard properties of a 2005 dwelling under Part L. From this base one must demonstrate the
improvement.
The reference dwelling consists of 27 parameters and these are set out in Appendix C of the TGD. It is
believed, almost universally in the industry (presumably through DEAP training) that the reference dwelling
measures the performance of the actual dwelling being tested under 2005 regulations. However, this is not
the case.
In 2005 research was carried out to define this ‘reference dwelling’. A study of the performance of nine
common housing types with 2005 regulation standards was carried out by the RIAI. It was found that on
average they performed similarly to the medium size semi-detached house, and this was, therefore, chosen
a the basis for a ‘reference dwelling’.
Though 24 of the parameters have been fixed, in the case of three of the parameters, the figures for the
actual dwelling being tested are entered. These all relate to the form of the building.
For example, the reference dwelling always has one chimeny regardless of how many are in the actual
dwelling. It always faces E/W, has natural ventilation, mains gas heating etc… Additionally the area of
windows is always defined as 25% of the floor area. These parameters are all taken from the medium
semi-d described above.
However, rather than keep with the above logic and define the roof area as 50% of the total floor area (which
it is in the case of the medium semi-d), the reference dwelling assumes the actual area of the roof on the
dwelling being tested.
As a result, a building which is more efficiently formed, performs to a higher standard of energy efficiency in
the reference dwelling, and therefore, when this level of energy use is multiplied by the MPEPC of 0.4, it is
tasked with a higher target level of energy efficiency (see graph 1).
This situation is highly unsatisfactory as it penalises those who design in an efficient manner, which is
contrary to the ambition of the Part L, which is to promote energy efficient buildings.
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Graph.1 -
Illustrating Change in Target Energy Use of Dwellings with Different Forms
under the MPEPC Methodolog
Note that this does not require that individual dwellings demonstrate a 60% improvement on 2005 standards.
This point has been confirmed by the DoEHLG. Additionally, as the reference dwelling is largely a standard
house type, the MPEPC does not demonstrate improvement levels of individual houses compared to 2005
standards.
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Part L Regulation.
The Part L regulation states: “For new dwellings, the requirement of L1 shall be met by providing that the
energy performance of the dwelling is such as to limit the calculated primary energy consumption and related
CO2 emissions … when both … are calculated using the Dwelling Energy Assessment Procedure (DEAP)
published by Sustainble Enegy Ireland.”
Note that the regulation makes no mention of the use of 60% energy reduction targets or MPEPC
methodologies. Compliance is to be demonstrated in terms of primary energy consumption and CO2
emissions using DEAP. DEAP measures these in terms of kWh/m2/yr and kgCO2/m2/yr.
The RIAI submit that expressing the requirement for compliance in terms of kWh/m2/yr and kgCO2/m2/yr
would be more closely in keeping with the requirement in the regulation.
EPBD Building Directive.
This directive allows each country to develop their own methodology and targets, in relation to energy
efficiency in buildings. Ireland’s targets are as set out in the Programme for Government and the
methodology is the DEAP.
Therefore, the RIAI proposal is not in contradiction of any policy or regulatory context.
Impact on DEAP:
Currently DEAP is available for download from www.seai.ie in two different formats. Both of them use the
kWh/m2/ye and kgCO2/m2/yr measures as the primary means of calculating the energy performance of the
dwelling. Only one version of the DEAP contains the MPEPC/MPCPC function.
The RIAI proposal would have little effect on DEAP as it is currently fully available without the MPEPC
function, and it expresses results in the manner proposed by the RIAI.
It is submitted that the amendment would have little impact on DEAP assessors as the proposal does not
add any new function. The method of presenting results would revert to being the same as in existing
dwellings, so, if anything, it would make the process less complicated for assessors.
A. Levels of Thermal Comfort.
There are limitations to the DEAP methodology and TGD assumptions regarding thermal comfort which must
be considered. There are standard assumptions e.g. the main living space is heated to 21oc though the
heating season. This could be considered quite a high temperature and the reduction of this to say 18 oc
would provide a reduction in energy consumption. Currently there is no facility in DEAP to identify this as a
potential energy saving measure, nor is there any examination of what constitute acceptable thermal comfort
levels in dwellings within the TGD. As the standards of fabric improve the thresholds of thermal comfort will
also improve. For example, as walls become well insulated the surface temperature will not be that much
greater than the ambient temperature, thus the sensation of thermal comfort will be maintained at a lower
temperature.
B. Metric of kWh/m2/yr & C02/m2/yr
Another major limitation of DEAP and the TGD in assessing individual dwellings, in terms of energy
performance, is the measure of kWh/m 2/yr & to C02/m2/yr assess compliance.
Take the example of comparing House 1: 500m 2 A3 rated consuming 65kWh/m2/yr and House 2: 75m 2 D1
rated consuming 250kWh/m2/yr. House 1 consumes 32,500kWh/yr which is 1.7 times that of House 2 at
18,750kWh/ m2/yr yet ostensibly appears more energy efficient, which is very misleading. Very small houses
should have some compensation in Part L compliance to acknowledge their actual lower energy use.
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E. Renewable Technologies
The RIAI propose that the requirement for on-site renewables be altered from an absolute figure to a
proportional one, i.e. that 10% of the energy demand of a dwelling is supplied by renewables.
This policy has been very successful in the UK (The Merton Rule) as it encourages a developer to construct
to a standard in excess of the regulations as a means of reducing the quantity of renewables required. As it
is proposed to further increase energy efficiencies of Part L in 2013, and as retrofitting is expensive and of
variable success, there should exist an incentive to construct to the highest possible standards. Take the
example of a Passive House: it has a maximum Energy demand of 15kWh/m2/yr without resorting to
additional renewable heating measures. The principle being – reduce the heating demand through the fabric
of the building, and maximize the heat gains through solar radiation and internal heat gains.
Additionally micro renewables are an expensive abatement technology and regulations which would
encourage their installation in non-optimal locations should be avoided. We would recommend that
renewables be required in 'all reasonable circumstances'.
Finally we would recommend that following the logic applied to solid-fuel stoves and heat pumps. They
should be excluded from the list of renewable technologies because both are only partially renewable,
dependent on circumstance, and therefore should be treated the same.
3. Commentary on Specific TGD provisions :
New Dwellings:
1.2
Renewable Energy Technologies:
1.3
Building Fabric.
1.3.1
General.
This section should include further strongly worded advice making it very clear that the maximum
elemental U-values are very conservative and in reality would need to be much lower to achieve the
required EPC & CPC.
1.3.2
Fabric Insulation.
1.3.2.4 DayLight Factor.
BS 8206: Part 2: 2008 Code of Practice on Daylight.
The Daylight factors recommended here are very conservative and could result in buildings with small
windows to increase the thermal efficiency but require electrical lighting on for a large proportion of the day.
The BS recommends the following daylight factors:
Bedrooms
Living rooms
Kitchens
1%
1.5%
2%
The Chartered Institution of Building Services Engineers (CIBSE) 1987 advises that when the average
Daylight Factor is less than 2%, the interior would be perceived as badly lit and artificial lighting could be
utilized constantly. Instead a DF exceeding 5% on the horizontal plane is required for a room to look bright.
The current standard is undesirable both from the point of view of reducing electrical demand but also from
the occupants point of view i.e. potentially dull and gloomy rooms. Provision of optimum daylight as a
passive energy strategy to reduce the use of electricity should not be overlooked in the statutory design
requirements of dwellings in Ireland.
Proposal: The daylight factor should be increased to 5%.
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Section 4: Existing Dwellings.
4.1 DEAP Review.
While the RIAI as part of the review of DEAP, has an intrinsic relationship with the Part L and it was therefore
felt appropriate to make comment on several software issues in this submission.
Calculating U-Values:
The DEAP review guidance should reference acceptable software for the calculation of U-Values. As the
guidance has moved away from standard U-Values, it will be less common to use the exact same U-Values
from project to project, and the practitioner will have much more occasion to calculate these. Ideally the
DEAP software should include a tab for recording fabric build up and calculating U-values.
Calculating Thermal Bridging:
In addition measured thermal bridges should be included as a tab within the software.
Part F Compliance:
The RIAI suggest it would be useful for DEAP to contain a tab to record details of ventilation provided and a
facility to demonstrate compliance with Part F.
Thermal Comfort:
Software should enable designer to set appropriate levels of thermal comfort in terms of internal
temperatures within defined parameters as part of the overall energy performance strategy.
Concluded: 12.01.2011 - RIAI
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