CATEGORIES 1 AND 2 OF THE CODE FOR SUSTAINABLE HOMES Energy and CO 2 Emissions, and Water

Transcription

1 CATEGORIES 1 AND 2 OF THE CODE FOR SUSTAINABLE HOMES Energy and CO 2 Emissions, and Water We saw last month that the Code for Sustainable Homes is based on assessing the sustainability of a new home by awarding points under nine categories. These categories range from the most important, Energy and CO 2 Emissions (maximum points: 36.4), to the least important, Surface Water Run-off (maximum points: 2.2). There are mandatory requirements (ie, minimum standards) in some of the categories, too. The sum of the points for the nine categories determines the Code Level according to the table in last month s article. For Code Level 1, the home has to be awarded at least 36 points, and for Code Level 6 at least 90 (out of the 100 available). Gaining credits and scoring points The scoring of points is a two-stage process. Credits are awarded according to the performance of the new home with respect to various issues within each category. The sum of the credits is multiplied by the conversion factor for that category to give the number of points awarded. For some issues, the requirements are easily met. For others, meeting the requirements may be too onerous or too costly either in the substance of the requirement (eg, using responsibly source materials), or in the certification necessary (eg, having the certification for the materials used). Likewise, for some issues the methodology for determining the credits is simple, for others complex. Let s now look at how to gain credits and score points in Categories 1 and 2. (Other categories will follow in later articles.) I m painting the picture below with broad brush-strokes. If a formal Code assessment will be required, then check out the fine details in the Technical Guide see Further Info. Or leave the matter to your Code assessor and architect. If no formal assessment will be required but you still want to build green, you may like to simply skim through this and the following articles in order to become familiar with the issues that need your consideration. CATEGORY 1 ENERGY AND CARBON DIOXIDE EMISSIONS Maximum number of credits in this category: 31. One credit converts to 1.17 points, so the maximum number of points is There are eight issues to be considered in this category, as below: Dwelling Emission Rate Aim: To limit CO 2 emissions arising from the operation of a dwelling. Credits available: 10. Mandatory at Code Levels 4, 5 and 6. The Target Emission Rate (TER) and the Dwelling Emission Rate (DER) are calculated within SAP2009 (a methodology required by Part L1A of the building regulations). The TER is the maximum rate allowed (per square metre of floor area) for the CO 2 emissions arising from space and water heating, ventilation, and lighting. The DER is the actual rate of these CO 2 emissions, according to SAP2009. CSH CATEGORIES 1 AND 2 1 APRIL 2011.

2 The percentage improvement (if any) of the DER over the TER determines the credits awarded, as in the table: % Improvement of DER Zero Net CO 2 Emissions Credits Level at which mandatory Credits for a low Dwelling Emission Rate (DER) If the DER is 100% better than the TER, then the Dwelling Emission Rate = 0. How can Zero Net CO 2 Emissions, as in the table above, be better than this? The answer is that Net CO 2 Emissions includes the emissions associated with the use of appliances (including cooking). So for Zero Net CO 2 Emissions, your home will have to produce over a year enough electricity to run the appliances, as well as that required for space and water heating, ventilation and lighting. Note the mandatory requirements. For example, for a home to achieve Code Level 4, the Dwelling Emission Rate must be at least 25% lower than the Target Emission Rate no matter how well the home performs in other respects. Fabric Energy Efficiency Aim: To improve fabric energy efficiency in order to future-proof CO 2 reductions for the life of the dwelling. Credits available: 9. Mandatory at Levels 5 and 6. It is easy to beat the TER by heating your home with a wood or pellet stove (or boiler). But at some time in the future that stove might be changed for electric or gas heating so the Code requires your home to be well insulated anyway. (Nor should wood be consumed unnecessarily.) The Fabric Energy Efficiency is a measure of how well/badly the home is insulated. It is defined to be the energy demand over a year for space heating (and cooling) in kwh per square metre of the fabric (envelope), and is an output from the SAP worksheet. Unfortunately, the word being used, Efficiency, is a misnomer. For any sensible application of the word, the higher the efficiency the better. In this case, the higher the so-called Fabric Energy Efficiency, the worse. Inefficiency would have been a more appropriate word! Fabric Energy Efficiency (kwh / m 2.year) Credits Level at which mandatory 5, 6 Energy Display Devices Credits for energy efficient 'fabric' (or 'envelope') Aim: To promote the use of equipment to display energy consumption. An electricity monitor costs about 40 a few electricity suppliers provide them free to customers. The display inside the dwelling shows occupants the current usage of CSH CATEGORIES 1 AND 2 2 APRIL 2011.

3 electricity, the tariff, etc. (The display is controlled wirelessly from a device that clips around a thick wire in the meter box.) You get one credit for an electricity monitor. You get another credit if electricity is the primary heating fuel. If not, you can get the extra credit if you have a monitor for the primary heating fuel, eg, gas but monitors for gas (or oil) are not yet available. Drying space Aim: To promote the drying of clothes with reduced energy. Credits available: 1. To get the one credit available, install 6m of clothes line/s. (If the lines are installed indoors, an extract fan must be present, as in a utility room or bathroom.) Energy Labelled White Goods Aim: to promote the use of energy efficient white goods. The simplest way to get both credits is to have all of the following: A+ rated fridge and freezer (or fridge/freezer). A rated washing machine and/or dishwasher. Information available about the EU Energy Efficiency Labelling Scheme. (Labels range from A++ to G.) External lighting Aim: To promote energy efficient external lighting. There s one credit available for appropriate security lighting (eg, movement detection by a PIR sensor, and switched on for a short duration). If there is no security lighting, you may get this credit by default. From the sustainability perspective, not having security lighting is credit worthy. Another credit is available for space lighting with: Energy efficient fittings though the demise of tungsten filament bulbs probably means that such fittings are unnecessary. An appropriate control system eg, always off during daylight. Strangely, if there is no space lighting, there is no default credit. Low and Zero Carbon Technologies Aim: To reduce the CO 2 emissions and running costs incurred in the operation of a dwelling by encouraging the installation of low and zero energy sources. CSH CATEGORIES 1 AND 2 3 APRIL 2011.

4 If the use of low carbon technologies results in 10% lower emissions, you get 1 credit; a 15% reduction results in 2 credits. And rather surprisingly, that s the most you can get. The technologies eg, PV panels, solar thermal collectors, a microchp unit, or a heat pump must be MCS certified. (MCS = Microgeneration Certification Scheme.) To determine the reduction, the net CO 2 emissions for a Standard Case are calculated in SAP2009. The main assumptions for this hypothetical Standard Case are: Gas is used in a condensing boiler for space and water heating. Central heating is installed with radiators and appropriate controls. Hot water is stored in a 150 litre cylinder with 35 mm of foam insulation. Based on what is actually installed, the net CO 2 emissions for the Actual Case are likewise calculated. The percentage improvement over the Standard Case determines the credits gained. Cycle storage Aim: To promote the wider use of bicycles. To encourage us all to cycle, we need storage space for cycles. A shed may suffice, but an even easier way to gain a credit or two is to allocate part of your garage for cycle storage. There must be enough space for both the car(s) and the bike(s). Home Office Number of bedrooms 2 or 3 4 or more Cycle storage spaces or 3 4 Credits Credits for cycle storage spaces (Dependent on the number of bedrooms in the dwelling.) Aim: To promote working from home. Credits available: 1. The plans for your house may not indicate a Home Office, but it s fairly easy to pick up the one credit allowed here. You can turn a bedroom, a study, or some other suitable room into a Home Office simply by installing a phone/broadband socket. (An extra detail: the room must have adequate daylighting. The Technical Guide has a complex formula for calculating this. More generally, daylighting is an issue in Category 7 Health and Well-being.) CATEGORY 2 WATER Maximum number of credits: 6. One credit converts to 1.5 points, so the maximum number of points is 9. CSH CATEGORIES 1 AND 2 4 APRIL 2011.

5 Indoor water use Aim: To reduce the consumption of potable water. Credits available: 5. Mandatory at all Levels. In my February article about recent revisions in the building regulations, we saw that the 2010 Part G requires the consumption of wholesome water to be no more than 125 litres/day per person (as calculated by the Water Efficiency Calculator for New Dwellings). You can gain credits by beating that figure: Calculated consumption (litres/day per person) Credits Code Level at which mandatory 1, 2 3, 4 5, 6 Credits for low water consumption You can probably reduce consumption down to the mandatory figure for Code Level 3 (105 litres/day per person) by fitting water-efficient WC s, taps, showers, washing machine and dishwasher, and a low volume bath. (I ll be writing about water efficiency later in the year.) Wholesome (as in Part G) and potable (as in the Code) seem to have the same meaning: drinking quality. External water use Aim: To promote the recycling of rainwater. Credits available: 1. You get a credit if there is provision for watering the garden with harvested rainwater. If you do not have a rainwater harvesting system, a suitably-sized rainwater butt will suffice. Garden pool? Swimming pool? Hot tub? Unless the water for these is harvested rainwater (or treated grey water), the credit cannot be awarded. Next month: Categories 3 and 4 Materials, and Surface Water Run-off. FURTHER INFO: Code for Sustainable Homes Technical Guide, November 2010 Free download from: Efergy Elite Which? best buy electricity monitor ( 40). Water Efficiency Calculator for New Dwellings Online calculator: CSH CATEGORIES 1 AND 2 5 APRIL 2011.

6 Words Copyright article by Robert Matthews in SelfBuild & Design magazine, April, CSH CATEGORIES 1 AND 2 6 APRIL 2011.