1. Solar Gain The ultimate free lunch!

2. Some Basics Why do we need to heat our homes? –Living rooms21 o C –Bedrooms18 o C –Staircases & halls16 o C

3. Heat Flow 1 st Law of Thermodynamics – conservation of energy – heat = work = energy 2 nd Law of Thermodynamics –Heat flows from a hotter body to a colder body (unless work is expended) –Entropy increases

4. Energy Flow – U Values Q f = UA(T 1 -T 2 ) –Q t = Rate of heat transfer in Watts –A = Area in m 2 –T 1 -T 2 = Internal temp – external temp –U = Overall thermal transmittance co-efficient in W/m 2 o C L = thickness in m k = thermal conductivity W/m o C R = resistance of surface in m 2o C/W

6. U Values Walls –Cavity wall – air void1.5 W/m 2 o C –200mm cast concrete3.1 W/m 2 o C –150mm cast concrete3.5 W/m 2 o C Windows –Single glazed5.6 W/m 2 o C –Double glazed 6mm 3.4 W/m 2 o C –Double glazed 12mm3.0 W/m 2 o C

7. Typical Insulated Masonry wall types to achieve a U-value of 0.27W/m 2 degK or better.

8. 95mm Aerobord Platinum will give a U-value of 0.27 W/m 2 degK when used in this wall type.

9. 65mm Aerobord Platinum in the cavity and 25mm Aerobord Platinum internally will give a U-value of 0.27 W/m 2 degK. If the internal insulation is increased to 65mm the U-value will be reduced to 0.21 W/m 2 degK.

10. 65mm Ecotherm PIR (Polyisocyanurate) Board fixed internally will give a U-value of 0.27 W/m 2 degK.

11. 95mm Aerobord Platinum cavity fill insulation will give a U-value of 0.27 W/m 2 degK when used in this wall type. 105mm Blown Aerobord Platinum bead will give a U-value of 0.27 W/m 2 degK when used in this wall type. When cavity insulation is increase to 150mm a figure if 0.20 W/Mm 2 degK is achieved.

12. 65mm Ecotherm PIR (Polyisocyanurate) Board fixed internally will give a U-value of 0.27 W/m 2 degK.

13. Thermal loss and gain is not steady state process

14. Solar Energy Solar radiation –0.9 kW/m 2 –Varies with Latitude Time of day and year Atmospheric clarity Orientation of surface –Direct, Diffuse or Reflected

15. Passive Solar Design Heating, Lighting and ventilation! Not just heating In a typical office 40% of energy usage can be due to lighting, in other cases 40% can be used by air conditioning

16. Catching some rays! Photovoltaic cells –Expensive – but developing technology, watch this space! Water based collectors – matt black pipes in a shallow glazed box Passive collection

17. Problems? The sun doesn’t shine at night! When the sun isn’t shining it’s cold! When the sun is at its hottest you don’t want to heat your house

18. Greenhouse Effect How does a greenhouse work? –Think of a car on a hot day Radiated heat is allowed in and warms the contents of the greenhouse, in hot weather the rate of gain is higher than the rate of loss, hence the temperature increases

19. Heat Transfer - Mechanisms Conduction Convection Radiation

20. Windows

21. Window Design - Climate dependant U Values Low-emissivity (Low-E) coatings –control heat transfer through windows with insulated glazing –Low-E coatings typically cost about 10%–15% more than regular windows, but they reduce energy loss by as much as 30%–50%. Solar Heat Gain Coefficient –Low SHGC, less solar heat transmitted, good shading –High SHGC, good for collecting solar heat gain during the winter. Visible Transmittance – how much light is let in Spectrally selective coatings –filter out 40%–70% of the heat normally transmitted through insulated window glass or glazing, while allowing the full amount of light to be transmitted. Light-to-solar gain (LSG) –ratio between the SHGC and VT. The higher the number, the more light transmitted without adding excessive amounts of heat.

22. Direct Solar Gain

23. Thermal Mass

24. Indirect solar gain

25. Thermosiphon

26. Overhangs & Shading & Shelter Overhangs –Can reduce effect of summer sun Want to let winter rays in Shelter can help reduce heat loss

27. Overhangs & Shading

28. Example

29. Orientation

30. Example 1

31. Example II

32. Example III

33. Southfacing

34. Passive Solar Design is location dependent!!! Previous examples were Californian Glazing - dilemma – Potential gain in radiated heat – Potential loss through lower thermal performance

35. Sunrooms

36. Importance of Shelter Deciduous trees’ bare branches allow sunlight to filter through in winter

37. Potential Energy Savings – Estate in UK

38. Principal glazed elevation facing south

40. Latitude

41. Overshading – minimum spacing

42. House spacing – Latitude

43. Site topology is a factor

44. Avoid self-shading

45. Be aware of potential shading due to unnecessarily steep pitch

46. Avoid Garages on the south side

47. Minimising overshading

48. Vegitation – privacy and light effects

49. Typical Characteristics of Passive Solar houses

50. Preferable house layouts

51. The truth Reduce area of North, East and West facing glazing – heat loss is always greater than loss of solar gain (even with low emissivity glass)– keep at 15% of floor area to give adequate lighting In sites with good solar exposure – areas of south facing double glazing are thermally neutral. Slightly negative in colder areas and positive in more southerly sections of the UK. If low emissivity glass is used then south facing glazing will be thermally positive over most areas of the UK A passive solar house typically has between 60% and 75% of its glazing on its southern aspect