Online Seminar Questions - Energy
To help you understand the Code for Sustainable Homes, The Concrete Centre and our technical team have produced answers to the questions we have recieved from the online seminar.
This section will cover all general questions relating to the Energy section of the Code.
1. "How does the Code relate to SAP 2005 and the Energy Performance Certificates - which will you need to show compliance to?"
Response - Colin Marshall, Tarmac Topblock: "At present the Code for Sustainable Homes is voluntary for all except Government funded dwellings. The SAP 2005 energy calculation is an integral part of showing compliance with Part L of the Building Regulations. It is used to calculate the Target (TER) and Dwelling (DER) carbon emission rates and is required to be produced by an accredited energy assessor. You will still be required to show compliance with the Building Regulations using SAP 2005 but the Regulations will be improved to match the varying Code levels in stages over the coming years (up to Level 6 zero carbon in 2016). Energy Performance Certificates (EPCs) are a requirement of the Home Information Pack (HIP) Regulations and will be produced by the SAP assessor upon completion as a statement of the energy performance of the dwelling. You are probably aware that that the requirements for HIPs are currently suspended but will be phased in from August 2007."
2. "What does TER and DER stand for?"
Response - Colin Marshall, Tarmac Topblock: "Firstly may we apologise for using abbreviations that we did not explain fully during the presentation. The TER and DER refer respectively to the Target Emission Rate and the Design Emission Rate. These are terms used in the SAP Energy Calculation procedure which is used to demonstrate compliance with Part L1 (new dwellings) to the Building Regulations. The TER is calculated for each dwelling and is expressed as an overall heat loss (W) per square metre of floor area. The dwelling is then designed so that its DER does not exceed the TER."
3. "Is the 25% CO2 improvement achieved for flats through renewables per individual unit or can it be a lump sum averaged out over the whole block of flats?"
Response - Colin Marshall, Tarmac Topblock: "Assessment will be required for each dwelling type on a development and not necessarily each individual dwelling.
A Dwelling Type is defined as dwellings having
- the same size, built form and construction details
- same space and water heating and controls
- same orientation and level of over shading, and
- same assumed/actual air permeability and ventilation system.
The Code does allow for area weighted average reductions to be used for buildings containing multiple dwellings. However, this is restricted to dwellings of the same type - so for a block of flats ground floor units would represent one type, mid floor units another and top floor units a third. Similarly, a mid-terrace and end-terrace unit of the same house type would be classified as two Dwelling Types."
4. "What are the benefits of using masonry construction in meeting the Code requirements?"
Response - Colin Marshall, Tarmac Topblock: "Enhanced energy / CO2 and sound insulation performance can be achieved using Tarmac Topblock products in external and separating wall constructions respectively, thus gaining points towards the required Code Level. The materials section encourages the use of constructions with low environmental impact and Tarmac Topblock constructions can be specified, to wall and floor (beam and block) elements, with many solutions achieving an 'A' rating according to BRE's Green Guide to Housing. There are also many indirect benefits to consider. Tarmac Topblock's masonry is inherently durable and can contribute towards resilient construction thus mitigating the risk of flooding (Category 4 - Surface Water Run-off). The adaptability of Tarmac Topblock masonry can be used to benefit in meeting the standards of Lifetime Homes (Category 7 - Health and Well-being)."
5. "The Energy category has a minimum standard at every Code Level. Will the basic Tarmac Topblock wall / floor construction have to change?"
Response - Colin Marshall, Tarmac Topblock: "The contribution to the energy equation from walls and floors or other building elements will not be as significant as previous changes to the thermal regulations, but it is inevitable that some improvements will be required to contribute to the overall solution. For meeting the higher code levels U-values of walls down to 0.20W/m²K are anticipated. Improvements to wall and floor constructions are available that will make a valuable contribution to achieving the requirements, although higher Code levels will not be obtainable without the use of renewable energy and changes to how the internal environment of homes is controlled."
6. "As a social housebuilder needing to comply with NHBC all our cavities must be at least 50mm clear. None of your examples for Code Level 3 compliance show this-can you suggest a wall make up to achieve U 0.25W/m2K on a 100mm cavity with 50mm clear ventilation?"
Response - Colin Marshall, Tarmac Topblock: "It certainly becomes more challenging to meet lower u-values using current constraints on cavity width etc. However a typical solution using Durox (or Toplite equivalent) would be:
Facing brick, 50mm clear cavity, 50mm Kingspan Kooltherm K8 partial fill, 100mm Durox Supabloc 3.6N, plasterboard of lightweight plaster finish internally.
U-value = 0.25W/m²K
There may be other requirements, such as a need for a higher strength block, or perhaps a flanking sound insulation requirement, which may require the use of an alternative Topblock product. If you have any additional specification requirements please advise and we will confirm or otherwise compliance."
7. "Is it feasible to construct social housing at Code 4 based on the construction skills/materials available now?"
Response - Colin Marshall, Tarmac Topblock: " The Energy performance Category of the Code is probably the most demanding in terms of the changes (and costs) that will be required compared to current Building Regulation Part L1 requirements. Code Level 4 represents a 44% reduction in the Dwelling Emission Rate compared to current Part L standards. Although it should be possible to achieve these levels with technologies currently available, it will not be possible to do so without introducing some renewable energy technologies. Therefore, in addition to improved fabric U-values and lower levels of air permeability, energy technologies such as solar water heating, photovoltaic panels and low emission heating such as biomass fuel, ground or air source heat pumps or combined heat and power (CHP) units will have to be considered on building projects.For compliance with the other design Categories, enhanced performance in many areas is already achievable. The Code (Pages 25- 27) does contain some Practical Examples at what typical measures are required to meet Code Levels 1, 3 and 6."
8. "If you are making the property more airtight as the Code level goes up what is the effect of condensation for Code Level 5/6?"
Response - Colin Marshall, Tarmac Topblock: "It is inevitable that to meet the energy performance of Code Level 5 and 6 that the airtightness of the structure will have to be continuously improved. In the Code for Sustainable Homes presentation our Ian Gray intimated that at these levels some form of mechanical heating and ventilation system would have to be considered. Certainly this has been our experience on some of the low energy projects that have already been constructed in the UK where we have been involved. It may be of some comfort to know that there is in place industry working groups ( which include masonry designed houses) that are looking at what a Code 5 or 6 house may look like including the energy and ventilation requirements. Part of this work has included looking at experiences from abroad such as low energy housing in Germany. Our industry is acutely aware of the need to avoid the harmful effects of condensation as well as maintain good internal air quality. I am confident that the guidance will be in place for mainstream housing to meet future requirements."
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