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General: Any SAP guru's in?

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  1.  
    • CommentAuthorchriskemp
    • CommentTimeJul 8th 2012
     
    I understand the principles of SAP, but have never completed one personally.
    I am trying to put a shopping list of components (not manufacturers) and values/variables - for the elements required for a SAP calc.
    Can you guys/gals help me fill out said list.

    i.e

    ventilation (type/sfp/efficiency)
    windows (uValue)
    doors (uValue)
    orientation of dwelling
    footprint / volume of dwelling
    low energy lighting / percentage
    low water consumption taps etc
    uValue of walls
    uValue of floor
    uValue of roof
    method to heat water?
    airtightness

    what variables have I missed?
    • CommentAuthorGaryB
    • CommentTimeJul 8th 2012
     
    Chris:

    You will also need the following:

    1. Heating system type and controls proposed / fitted (timed, zone control, load & weather compensation)
    2. Window frame material - this will affect the frame factor for solar gains
    3. Details of any renewables fitted

    It is usually best to use manufacturer's data if available as the default values in SAP are normally conservative.

    BTW, low water flow fittings are not required for SAP but are a CSH requirement. This is an oversight in my opinion.
    • CommentAuthorchriskemp
    • CommentTimeJul 8th 2012
     
    Thank You gary.

    Have we got all the boxes covered now?
    • CommentAuthorGaryB
    • CommentTimeJul 8th 2012 edited
     
    Drawings will be needed as the area of windows and the orientation of the walls in which they are fitted will be required to complete the SAPs.
    • CommentAuthorchriskemp
    • CommentTimeJul 8th 2012
     
    so, in essence to complete a SAP calc' we need to know the following parameters & values:

    ventilation (type/sfp/efficiency)
    windows (uValue)
    area of windows / orientation of
    doors (uValue)
    orientation of dwelling
    footprint / volume of dwelling
    low energy lighting / percentage
    uValue of walls
    uValue of floor
    uValue of roof
    method to heat water?
    airtightness
    Heating system type and controls proposed / fitted (timed, zone control, load & weather compensation)
    Window frame material - this will affect the frame factor for solar gains
    Details of any renewables fitted

    ought else?
    • CommentAuthorGaryB
    • CommentTimeJul 8th 2012
     
    Should cover it!
    • CommentAuthorchriskemp
    • CommentTimeJul 8th 2012
     
    cool.
    cheers ears.

    I shall now work on the product spec's to add values to the parameters... starting with a 0.1 uValue for walls and roof ;-)
    • CommentAuthorneilu
    • CommentTimeJul 8th 2012
     
    The SAP assessor will need to be able to work out the areas of each exposed element (walls,openings,etc) from the drawings so they will needto be of a suitable standard, ie dimensions construction plans, sections and elevations.
    Ideally the SAP assessor will need to be able to work out the areas/construction of internal walls and floors/ceilings to calculate the thermal mass. The construction of the external walls/roof will also affect the thermal mass calculation.
    Water efficiency - there is a a simple box to tick to say that the building will comply with current building regs (the water efficiency calculations are not overly hard to pass provided they are carried out before you buy the fittings, I've done a few that have failed).
    Extract ventilation - if you are simply using standard intermittent extract fans then we just enter the number of fans. For mechanical systems the assessor will need system details, be aware that even systems with heat recovery can be detrimental to the SAP.
    Can't think of anything else for now but I'll check when I get to work.
    • CommentAuthorSigaldry
    • CommentTimeJul 9th 2012
     
    A few more:

    - Address and Postcode (where it is makes some difference for summer overheating - will make more in the future).

    - Windows - full construction (Frame type (although doesn't make a huge amount of difference between wood and UPVC, but does for metal frames), air gap?, argon filled?, Emissivity?) not just U-value (and ensure it's U-window including frame, not center pane).

    - Same for glazed and for solid doors (and roof lights).

    - Overshading of the various windows? any overhangs?

    - It's load or enhanced weather compensation (not both), If underfloor heating, make sure you go for weather compensator (DHCG requirement), also if underfloor heating, is it underfloor under chipboard, in screed or in concrete (under chipboard comes out best responsiveness wise, followed by in screed).

    - Are emitters radiators or underfloor or a mix (e.g. underfloor downstairs, radiators upstairs).

    - If a heat pump, go with underfloor heating, make sure heating system adequately sized and doesn't require auxiliary heating or immersion if possible.

    - Is there any secondary heating proposed? What efficiency? What fuel type? Associated Chimney or Flue, or is it a balanced flue? Are you in a smoke control area?

    - What are all the heat-loss constructions (All assessors should be re-running the U-value calculations themselves, or ensuring that they've been done by someone competent). Ensure all heatloss constructions are included. Include sizes and centres of any bridges (frames / rafters / joists) and what materials.

    - What Thermal bridging details to be followed <- this one can make a massive difference.

    - Ventilation system - ensure if MEV or MVHR that the system is SAP Appendix Q rated.

    - Hot water Cylinder, size and manufacturers information & Model reference (preferably Manufacturers Declared Loss Factor for rate of heat loss per 24 hours).

    - Heating system - as much information as possible (make and model), so full information can be gotten from Product Characteristics Data File (SEDBUK). If not determined yet, specify type and minimum efficiency you are looking at (checking from www.SEDBUK.com that the specified efficiency is actually possible, rather than an exagerated claim). What fuel type?

    - Renewables - As much information as possible, where to be located, sizing, manufacturer make and model (Data sheets if possible).

    I can't stress enough how important good drawings are - preferably in a CAD format, or printed / drawn to scale if not. PDF's less use and more prone to error and photocopies can be worse than useless, especially if no dimensions shown to check scale unaffected.

    Hope the above helps.
    • CommentAuthorSigaldry
    • CommentTimeJul 9th 2012
     
    "BTW, low water flow fittings are not required for SAP but are a CSH requirement. This is an oversight in my opinion."

    Part G (2010) requirement is for new dwellings to be constructed to achieve no more than 125 litres per person per day of wholesome water, so It's better than it was.

    This also gives a 5% reduction to hot water demand in SAP 2009.


    Sigaldry
    • CommentAuthorchriskemp
    • CommentTimeJul 9th 2012
     
    fantastic
    Thank Sigaldry et al.
    • CommentAuthorDarylP
    • CommentTimeJul 9th 2012
     
    chriskemp,

    If you're looking for a good 'paper' SAP rating, play close attention to the Htb (heat loss through thermal bridges). The corresponding Y-value can be as low as 0.04, or as high as 0.15 if you do not supply Psi-values for the heat loss junctions.

    See -" What Thermal bridging details to be followed <- this one can make a massive difference." in the post above.

    This can make circa 15% difference in a pair of otherwise identical dwellings. However Psi-values are valid only for a particular detail. So whoever you get the Psi-values from, make sure they are valid.

    Cheers....:smile:
    • CommentAuthorchriskemp
    • CommentTimeJul 9th 2012
     
    Ta.
    I have the psi values for the building system i have in mind. Which have standard details for any project ;-)
    As low as 0.024 for party wall roof junction for example.
    • CommentAuthorDarylP
    • CommentTimeJul 10th 2012
     
    chriskemp,

    That's good then. If you want the SAP calc to show your dwelling in the best light, just get the App. K list tagged, and your'e done.
    Do you have the App. K list? If you need a set, email me, and I can let you have a copy.

    Cheers,:smile:
    • CommentAuthorbatkinson
    • CommentTimeJul 10th 2012
     
    you will of course have to provide the SAP assessor and your Building Control Body with evidence of how you have calculated the thermal bridges.
    • CommentAuthorchriskemp
    • CommentTimeJul 10th 2012
     
    cheers
    this is being done by BBS in Kent.

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