The following are the notes for a Design Advice session held with Energy Consultant David Olivier.  We found this session incredible helpful - albeit that some of that benefit does not show from these notes.

Design Advice Session.

Leominster, 13^th September 2002

Present:

David Olivier – Energy Consultant,

David Wadge – Client,

Neill Lewis – Architect.

The following minutes are bullet points of areas needing further consideration, monitoring or change and are not intended to document the full content of discussions.

1. General – use of beam and block floors will need closer attention to detailing to ensure air tightness of the construction. Other forms, such as precast planks or beam-and-pot, have already been ruled out by access and other factors.
2. Consideration – the support structure of the external insulation should be, if structurally feasible, increased from 400mm to 600mm centres. A "C" section was preferred for structural stability to an independent frame but materials for the web would be considered in terms of their thermal resistance as well as their strength. It would be beneficial to move away from a solid section in the "C" beams.
3. General – the potential weaknesses of installation of rigid plastic foam board insulation were discussed, compared to the generally good joints in fibrous material such as rock, glass or cellulose fibres. It was agreed that in the small number of places that foam (ZODP from Kingspan) will be used great attention will be given to this and joints will be taped with preferably an aluminium-based tape to ensure integrity of the join and reduce the potential for heat losses.
4. General – the internally insulated basement walls should have a polyethylene vapour barrier between the plasterboard and the insulation. To be detailed broadly as in Canada which has many basements and normally builds to a higher energy efficiency standard than the UK because of its colder climate.
5. Change – at ground level the cavity will be filled with Rockwool batts, provided structural stability can be maintained.
6. Change – basement drylined walls will have a framework of 75mm timbers mounted 50mm from the wall. This will allow for 125mm of Rockwool insulation, in two layers. This should have almost double the R-value, compared to solid 50 x 100mm battens mounted directly on the external wall, with 100mm Rockwool between the studs.
7. Consideration – the use of a lightweight block as a bearing for the concrete beams will need to be checked for load and spreaders used if necessary.
8. Change – basement floor will have insulation below screed and above slab, with insulation turned up at edges to butt into the insulation behind the drylining.
9. General – the design already incorporated a skirting of polyethylene sheet at wall/floor junctions to prevent air infiltration. These will use extra thickness sheets where they butt up against concrete to reduce damage.
10. General – when using polyethylene sheeting it will be sealed under the plaster using a strip of EXPM, to ensure air tightness.
11. Change – where T beams from 1^st floor broach the thermal envelope the spaces between the beams will be filled with in situ fine concrete, plastering will run right up to the soffit of the floor blocks and sealant will be used around the junction of the plaster and the floor structure, above the plaster stop bead.
12. Consideration and change – the current detailing of the roof allows a risk of significant air infiltration at the eaves. Thought needs to be given to whether or not a warm roof approach is to be used. If it is and a timber second floor is retained, as opposed to using a concrete one, as used on the European continent, detailing on the vapour barrier must ensure a continuous surface, which means sealing to each rafter. The rafters will be spaced at the maximum allowable distances and consideration given to a secondary system of rafters to reduce the number of junctions at the eaves. To carry out this to a reasonable standard is only realistic in the UK if one is using a self-build approach.
13. Change – windows will open inwards to improve the detailing of the large-section frames, if bespoke frames are to be used.
14. Consideration – maximise the glass area of each window rather than having many smaller windows. This may be achieved by use of 'false' mullions applied to the external face of a larger window.
15. Consideration – Scandinavian windows could be used of frame sections which make use of the best practice developed in Scandinavian countries, with mullions and transoms planted on as far as is necessary to meet the Planning Authority requirements. Nor-Dan and Sampson were suggested as two companies who have a good reputation for importing good quality products. Not all Scandinavian windows are equally good quality.
16. Consideration – French doors can be replaced by tilt and turn windows and hence gain a significant performance improvement (wider lights, fewer mullions and smaller bottom rail – hence admits more visible light and solar gains if required). This is common practice in Germany.
17. Consideration – Thermal performance of roof lights is poor, there maybe developments in the near future by the Metal Window Co., Oxon., makers of the galvanised steel Conservation Rooflight. Some Scandinavian suppliers (Tomo, formally imported into the UK) might be worth chasing.
18. Change – air tightness – a target is set of 1m³/m²/hr @ 50Pa with an expectation to achieve less that 2 m³/m²/hr @ 50Pa, with extreme attention to detail and workmanship. Some UK precedents exist – Embleton House in Twyford achieved about 1, Elizabeth Fry Building in Norwich about 2. A masonry house in Essex may have also achieved about 1 (based on measured fuel bills – leakage not yet tested).
19. Consideration – heat pump – check the refrigerant being used is ZODP.
20. Consideration – ventilation – high efficiency fans are more beneficial than high heat recovery in this country. A good target to aim for is 1W total per litre per second of fresh air input.
21. General – ventilation – minimise the length of cold duct runs between outside and ventilation heat exchanger (if possible no more than 1m), otherwise heat recovery performance drops significantly.
22. Consideration – heat pump – ensure high efficiency motor and control gear are used.
23. General – The spacing of the stainless steel wall ties [in the stonework] will be calculated to reduce the numbers of ties and hence heat paths.