16394 design: form and fabricnick kelly

1. 16394 Design: Form and Fabric Nick Kelly THIS LECTURE DEALS WITH THE GEOMETRY AND MATERIALS OF OUR BUILDINGS AND HOW THEY HAVE AN AFFECT ON THEIR ENERGY AND ENVIRONMENTAL PERFORMANCETHIS LECTURE DEALS WITH THE GEOMETRY AND MATERIALS OF OUR BUILDINGS AND HOW THEY HAVE AN AFFECT ON THEIR ENERGY AND ENVIRONMENTAL PERFORMANCE

2. IT IS THE PROPERTIES OF MATRIALS THAT INFLUENCE THEIR ENERGY AND ENVIRONMENTAL PERFORMANCE. THE MOST CRUCIAL OF THESE ARE: INSULATION (HOW WELL THE MATERIAL CONDUCTS HEAT) ; THERMAL MASS (MATERIALS ABILITY TO HOLD HEAT) THE TRANSPORT OF MOISTURE THROUGH THE MATERIAL THE GEOMETERY AFFECTS SOLAR ACCESS AND NATURAL VENTILATION (EXPLAINED LATER) IT IS THE PROPERTIES OF MATRIALS THAT INFLUENCE THEIR ENERGY AND ENVIRONMENTAL PERFORMANCE. THE MOST CRUCIAL OF THESE ARE: INSULATION (HOW WELL THE MATERIAL CONDUCTS HEAT) ; THERMAL MASS (MATERIALS ABILITY TO HOLD HEAT) THE TRANSPORT OF MOISTURE THROUGH THE MATERIAL THE GEOMETERY AFFECTS SOLAR ACCESS AND NATURAL VENTILATION (EXPLAINED LATER)

3. Fabric SO LETS LOOK MORE CLOSELY AT FABRIC PROPERTIESSO LETS LOOK MORE CLOSELY AT FABRIC PROPERTIES

4. U-value U-value (W/m2K) is a measure of how readily heat will flow through a material or structure: the lower the U-value the better a surface is insulated U-value is used to calculate the steady state heat flow through a construction A QUANTITY KNOWN AS THE U-VALUE IS THE BASIC MEASURE OF THE INSULATING PROPERTY OF A MATERIAL OR CONSTRUCTION. UNITS ARE W/m2K ACTUALLY COMPRISED OF A NUMBER OF ELEMENTS OUTSIDE SURFACE HTC, THICKNESS AND CONDUCTIVITY OF THE CONSTRUCTION LAYERS THE LOWER THE U-VALUE THE BETTER THE INSULATION PROPERTIES LOOK AT THE HEAT CONDUCTION EQUATION U-VALUE IS USED TO CALCULATE THE STEADY STATE HEAT TRANSFER THROUGH A MATERIAL THE TOTAL HEAT FLUX THROUGH A CONSTRUCTION IS THE PRODUCT OF THE SURFACE AREA U-VALUE AND THE TEMPERATURE DIFFERENCE ACROSS THE CONSTRUCTIONA QUANTITY KNOWN AS THE U-VALUE IS THE BASIC MEASURE OF THE INSULATING PROPERTY OF A MATERIAL OR CONSTRUCTION. UNITS ARE W/m2K ACTUALLY COMPRISED OF A NUMBER OF ELEMENTS OUTSIDE SURFACE HTC, THICKNESS AND CONDUCTIVITY OF THE CONSTRUCTION LAYERS THE LOWER THE U-VALUE THE BETTER THE INSULATION PROPERTIES LOOK AT THE HEAT CONDUCTION EQUATION U-VALUE IS USED TO CALCULATE THE STEADY STATE HEAT TRANSFER THROUGH A MATERIAL THE TOTAL HEAT FLUX THROUGH A CONSTRUCTION IS THE PRODUCT OF THE SURFACE AREA U-VALUE AND THE TEMPERATURE DIFFERENCE ACROSS THE CONSTRUCTION

5. Fabric problems[1]: thermal bridges common problems with constructions are ‘thermal bridges’ solution – disrupt high conductivity flow path with insulation LETS THINK ABOUT U-VALUES IN THIS COMMON BUILDING FABRIC PROBLEM (FOR BUILDINGS IN THE UK) – THE THERMAL BRIDGE IN THIS CASE A CONCRETE LINTLE FORMS A THERMAL BRIDGE TO OUTSIDE THE MAJORITY OF THE FABRIC AROUND THIS WINDOW IS WELL INSULATED, HOWEVER THE LINTLE FORMS A HIGH U-VALUE TO OUTSIDE HIGH HEAT LOSS – LOW INSIDE SURFACE TEMPERATURE RISK OF CONDENSATION THE SOLUTION TO THIS PROBLEM IS TO ADD INSULATION TO LOWER THE U-VALUELETS THINK ABOUT U-VALUES IN THIS COMMON BUILDING FABRIC PROBLEM (FOR BUILDINGS IN THE UK) – THE THERMAL BRIDGE IN THIS CASE A CONCRETE LINTLE FORMS A THERMAL BRIDGE TO OUTSIDE THE MAJORITY OF THE FABRIC AROUND THIS WINDOW IS WELL INSULATED, HOWEVER THE LINTLE FORMS A HIGH U-VALUE TO OUTSIDE HIGH HEAT LOSS – LOW INSIDE SURFACE TEMPERATURE RISK OF CONDENSATION THE SOLUTION TO THIS PROBLEM IS TO ADD INSULATION TO LOWER THE U-VALUE

6. U-value problems the constructions below have identical U-values but will give rise to totally different thermal performances NOW THE U-VALUE ALONE CANNOT TELL US ALL ABOUT THE THERMAL PERFORMANCE OF A CONSTRUCTION THESE TWO CONSTRUCTIONS HAVE THE SAME U-VALUE BUT TOTALLY DIFFERENT THERMAL PERFORMANCE ONE WOULD BE USEFUL IN A COLD CLIMATE THE OTHER BETTER SUITED TO A HOT CLIMATENOW THE U-VALUE ALONE CANNOT TELL US ALL ABOUT THE THERMAL PERFORMANCE OF A CONSTRUCTION THESE TWO CONSTRUCTIONS HAVE THE SAME U-VALUE BUT TOTALLY DIFFERENT THERMAL PERFORMANCE ONE WOULD BE USEFUL IN A COLD CLIMATE THE OTHER BETTER SUITED TO A HOT CLIMATE

7. Dynamic characteristics the U-value approach is actually a simplification of how heat flows with time through a material need to consider ‘dynamics’ for the concrete layer: U-VALUES ARE STEADY STATE BUT WE NEED TO THINK ABOUT DYNAMIC (TIME-VARYING CHARACTERSITICS) IF WE ARE TO FULLY UNDERSTAND HOW A CONSTRUCTION WILL BE HAVE THERMALLY THE DYNAMIC HEAT TRANSFER EQUATION FOR A SINGLE LAYER OF CONCRETE IS SHOWN EXPLAIN …. THERMAL CAPACITY IS A FUNCTION OF DENSITY AND SPECIFIC HEAT, HEAT PER UNIT AREA FLUX IS A FUNCTION OF TEMPERATURE AND CONDUCTIVITY (U-VALUE EQUATION IS A SPECIAL CASE!)U-VALUES ARE STEADY STATE BUT WE NEED TO THINK ABOUT DYNAMIC (TIME-VARYING CHARACTERSITICS) IF WE ARE TO FULLY UNDERSTAND HOW A CONSTRUCTION WILL BE HAVE THERMALLY THE DYNAMIC HEAT TRANSFER EQUATION FOR A SINGLE LAYER OF CONCRETE IS SHOWN EXPLAIN …. THERMAL CAPACITY IS A FUNCTION OF DENSITY AND SPECIFIC HEAT, HEAT PER UNIT AREA FLUX IS A FUNCTION OF TEMPERATURE AND CONDUCTIVITY (U-VALUE EQUATION IS A SPECIAL CASE!)

8. Thermal mass or more accurately ‘exposed thermal’ mass has a profound impact on how a building behaves THE THERMAL MASS OF THE BUILDING’S STRUCTURES IS AN IMPORTANT GOVERNING CHARACTERISTIC FOR THE DYNAMIC PERFORMANCE OF THE BUILDING THERMALLY MASSIVE MATERIALS INCLUDE CONCRETE, BRICK, STONE THERMALLY LIGHT MATERIALS INCLUDE CARPET, INSULATION, PLASTERBOARD LOW THEMAL MASS BUILDINGS RESPOND RAPIDLY TO HEAT INPUT (HEATING, SUN, PEOPLE EQUIPMENT) HIGH THERMAL MASS BUILDINGS RESPOND SLOWLY THE CONSTRUCTION ON THE RIGHT – MUCH OF THE HEAT GAIN IN THE BUILDING IS ABSORBED BY THE STRUCTURE (EXPOSED THERMAL MASS) – SO THE STRUCTURE HEATS UP RATHER THAN THE AIR INSIDE (HEATING SYSTEM AND WARM CLIMATE) THE CONSTRUCTION ON THE LEFT – INTERNAL HEAT GAINS IN THE BUILDING CAUSE THE AIR TO HEAT UP AS THE INSULATION PREVENTS THE THERMALLY MASSIVE MATERIAL ABSORBING THE ENERGYTHE THERMAL MASS OF THE BUILDING’S STRUCTURES IS AN IMPORTANT GOVERNING CHARACTERISTIC FOR THE DYNAMIC PERFORMANCE OF THE BUILDING THERMALLY MASSIVE MATERIALS INCLUDE CONCRETE, BRICK, STONE THERMALLY LIGHT MATERIALS INCLUDE CARPET, INSULATION, PLASTERBOARD LOW THEMAL MASS BUILDINGS RESPOND RAPIDLY TO HEAT INPUT (HEATING, SUN, PEOPLE EQUIPMENT) HIGH THERMAL MASS BUILDINGS RESPOND SLOWLY THE CONSTRUCTION ON THE RIGHT – MUCH OF THE HEAT GAIN IN THE BUILDING IS ABSORBED BY THE STRUCTURE (EXPOSED THERMAL MASS) – SO THE STRUCTURE HEATS UP RATHER THAN THE AIR INSIDE (HEATING SYSTEM AND WARM CLIMATE) THE CONSTRUCTION ON THE LEFT – INTERNAL HEAT GAINS IN THE BUILDING CAUSE THE AIR TO HEAT UP AS THE INSULATION PREVENTS THE THERMALLY MASSIVE MATERIAL ABSORBING THE ENERGY

9. Thermal mass can be used to ‘damp’ oscillations in the internal air temperature or limit peak temperatures when used in conjunction with ‘night’ flushing problematic in buildings that require fast thermal response THERMAL MASS HAS SOME USEFUL PROPERTIES – IT CAN BE USED A BIT LIKE A SPONGE TO SOAK UP EXCESS HEAT AT TIMES OF HIGH HEAT LOAD HEAT LOAWARMS THE SURFACE OF THE MATERIAL – THIS HEAT THEN TRAVELS TO THE COOLER INTERIOR OF THE MATERIAL AND THEN RE-RELEASE IT AT NIGHT WHEN TEMPERATURES FALL BELOW MATERIAL TEMPERATURE – DAMPING OUT FLUCTUATIONS IN TEMPERATURE – USEFUL FOR WARM CLIMATES Q: WHY WOULD A HIGH THERMAL MASS STRUCTURE BE A PROBLEM IS A DOMESTIC HOUSE IN WHICH THE OCCUPANTS SWITCHED ON THE HEATING INTERMITTENTLY? THERMAL MASS HAS SOME USEFUL PROPERTIES – IT CAN BE USED A BIT LIKE A SPONGE TO SOAK UP EXCESS HEAT AT TIMES OF HIGH HEAT LOAD HEAT LOAWARMS THE SURFACE OF THE MATERIAL – THIS HEAT THEN TRAVELS TO THE COOLER INTERIOR OF THE MATERIAL AND THEN RE-RELEASE IT AT NIGHT WHEN TEMPERATURES FALL BELOW MATERIAL TEMPERATURE – DAMPING OUT FLUCTUATIONS IN TEMPERATURE – USEFUL FOR WARM CLIMATES Q: WHY WOULD A HIGH THERMAL MASS STRUCTURE BE A PROBLEM IS A DOMESTIC HOUSE IN WHICH THE OCCUPANTS SWITCHED ON THE HEATING INTERMITTENTLY?

10. Thermal ‘lag’ heat transfer through an opaque material does not occur instantaneously – it is always associated with a time delay HEAT ALSO DOES NOT TRAVEL INSTANTANEOUSLY THROUGH A STRUCTURE – IT IS ASSOCIATED WITH A TIME DELAY AGAIN THIS TIME DELAY IS ASSOCIATED WITH THE MATERIAL PROPERTIES – CONDUCTIVITY, DENSITY AND SPECIFIC HEATHEAT ALSO DOES NOT TRAVEL INSTANTANEOUSLY THROUGH A STRUCTURE – IT IS ASSOCIATED WITH A TIME DELAY AGAIN THIS TIME DELAY IS ASSOCIATED WITH THE MATERIAL PROPERTIES – CONDUCTIVITY, DENSITY AND SPECIFIC HEAT

11. Passive Solar [1]: Trombe wall the Trombe-Michelle wall is a passive solar component that makes used of thermal mass and time lags to absorb and transmit solar radiation to the interior of a building SOLAR ENERGY IN BUILDINGS IS SOMETIMES A BIT PROBLEMATIC – ESPECIALLY IN SUMMER – WE GET THE ENERGY WHEN WE DON’T NEED IT – IN THE MIDDLE OF THE DAY A BUILDING STRUCTURE WHICH MAKES USE OF THERMAL CAPACITY AND THERMAL LAG TO GET ROUND THIS PROBLEM IS THE TROMBE WALL ABSORBS HEAT FALLING ON THE OUTSIDE OF A STRUCTURE IN THE MIDDLE OF THE DAY THIS PASSES THROUGH THE WALL OVER TIME AN ARRIVES IN THE EVENING WHEN HEAT IS NEEDEDSOLAR ENERGY IN BUILDINGS IS SOMETIMES A BIT PROBLEMATIC – ESPECIALLY IN SUMMER – WE GET THE ENERGY WHEN WE DON’T NEED IT – IN THE MIDDLE OF THE DAY A BUILDING STRUCTURE WHICH MAKES USE OF THERMAL CAPACITY AND THERMAL LAG TO GET ROUND THIS PROBLEM IS THE TROMBE WALL ABSORBS HEAT FALLING ON THE OUTSIDE OF A STRUCTURE IN THE MIDDLE OF THE DAY THIS PASSES THROUGH THE WALL OVER TIME AN ARRIVES IN THE EVENING WHEN HEAT IS NEEDED

12. Passive Solar [1]: Trombe wall THIS DIAGRAM SHOWS WHAT IS HAPPENING …. EXPLAIN THIS DIAGRAM SHOWS WHAT IS HAPPENING …. EXPLAIN

13. Vapour transport in addition to heat, moisture can also travel through the building fabric rate of moisture transport is related to the partial vapour pressure inside and outside the building just and in the case of different materials can have different moisture ‘conductivities’ permeable materials allow moisture to pass through easily impermeable materials act as a barrier to vapour TURNING FROM THERMAL CHARACTERSITICS TO VAPOUR TRANSPORT NOW IN ADDITION TO HEAT MOISTURE CAN ALSO TRAVEL THROUGH THE BUILDING FABRIC RATE OF MOISTURE TRANSPORT IS RELATED TO THE VAPOUR PRESSURE ACROSS THE STRUCTURE ARE ITS PERMEABILITY PERMEABLE MATERIAL – CONCRETE/BRICK IMPERMEABLE MATERIAL POLYTHENE – CAN ACT AS A BARRIER TO VAPOUR TURNING FROM THERMAL CHARACTERSITICS TO VAPOUR TRANSPORT NOW IN ADDITION TO HEAT MOISTURE CAN ALSO TRAVEL THROUGH THE BUILDING FABRIC RATE OF MOISTURE TRANSPORT IS RELATED TO THE VAPOUR PRESSURE ACROSS THE STRUCTURE ARE ITS PERMEABILITY PERMEABLE MATERIAL – CONCRETE/BRICK IMPERMEABLE MATERIAL POLYTHENE – CAN ACT AS A BARRIER TO VAPOUR

14. Fabric problems [2]: interstitial condensation in certain cases this can lead to condensation inside the construction when the local temperature falls below the local dew point temperature IN THE VAPOUR PHASE MOISTURE IS NOT A PROBLEM IN STRUCTURES BUT IN LIQUID PHASE (I.E. CONDENSED) IT CAN DEGRADE A STRUCTURE THIS CAN SOMETIMES OCCUR WHEN THE MATERIAL TEMPERATE FALLS BELOW THE DEW POINT TEMPERATURE WITHIN THE STRUCTURE CONSIDER THE CASE WITH A PERMEABLE INSULATING MATERIAL INSIDE THE BUILDING BACKING ON TO CONCRETE …. IN THE VAPOUR PHASE MOISTURE IS NOT A PROBLEM IN STRUCTURES BUT IN LIQUID PHASE (I.E. CONDENSED) IT CAN DEGRADE A STRUCTURE THIS CAN SOMETIMES OCCUR WHEN THE MATERIAL TEMPERATE FALLS BELOW THE DEW POINT TEMPERATURE WITHIN THE STRUCTURE CONSIDER THE CASE WITH A PERMEABLE INSULATING MATERIAL INSIDE THE BUILDING BACKING ON TO CONCRETE ….

15. Form LETS NOW LOOK AT HOW FROM AFFECTS ENERGY PERFORMANCELETS NOW LOOK AT HOW FROM AFFECTS ENERGY PERFORMANCE

16. Form: solar energy solar energy can be used in a building design to displace the need for both electric lighting and heating form of the building can be designed to maximise the use of beneficial solar energy the most basic renewable energy device is the window! WE’VE ALREADY LOOKED AT SOLAR ENERGY AND TROMBE WALLS HOWEVER THINKING MORE ABOUT THIS SOLAR ENERGY IS ONE OF THE BEST RENEWABLE ENERGY RESOURCES WE HAVE IT CAN DISPLACE ELECTRICAL ENERGY IN LIGHTING AND HEAT ENERGY FOR SPACE AND WATER HEATING WE CAN DESIGN A BUILDING TO MAKE BEST USE OF SOLAR ENERGY THE MOST BASIC SOLAR COLLECTOR IS THE WINDOW!WE’VE ALREADY LOOKED AT SOLAR ENERGY AND TROMBE WALLS HOWEVER THINKING MORE ABOUT THIS SOLAR ENERGY IS ONE OF THE BEST RENEWABLE ENERGY RESOURCES WE HAVE IT CAN DISPLACE ELECTRICAL ENERGY IN LIGHTING AND HEAT ENERGY FOR SPACE AND WATER HEATING WE CAN DESIGN A BUILDING TO MAKE BEST USE OF SOLAR ENERGY THE MOST BASIC SOLAR COLLECTOR IS THE WINDOW!

17. Form: glazing and orientation glazing is a transparent high conductivity, high speed energy flow path wall U-value 0.3W.m2K double glazing 2.0 W.m2K admits energy as s.w. solar radiation opaque to l.w. radiation loses energy through conduction/convection/radiation (l.w. & s.w.) south facing glazing is has a net energy gain north-facing glazing has a net energy loss GLAZING CAN BE AN ENERGY ASSET TO A BUILDING OR CAUSE ENERGY PENALTIES – DEPENDS UPON THE REQUIREMENTS ADMITS ENERGY IN THE FORM OF SW SOLAR RADIATION GLAZING HAS A HIGHER U-VALUE THAN THE REST OF THE STRUCTURE AND SO LOSES ENERGY THROUGH CONDUCTION CONVECTION AND LW RADIANT LOSS MUST BALANCE THE TWO SOUTH FACING GLAZING WILL GIVE A NET ENERGY GAIN NORTH FACING GLAZING WILL BE A NET ENERGY LOSER GLAZING CAN BE AN ENERGY ASSET TO A BUILDING OR CAUSE ENERGY PENALTIES – DEPENDS UPON THE REQUIREMENTS ADMITS ENERGY IN THE FORM OF SW SOLAR RADIATION GLAZING HAS A HIGHER U-VALUE THAN THE REST OF THE STRUCTURE AND SO LOSES ENERGY THROUGH CONDUCTION CONVECTION AND LW RADIANT LOSS MUST BALANCE THE TWO SOUTH FACING GLAZING WILL GIVE A NET ENERGY GAIN NORTH FACING GLAZING WILL BE A NET ENERGY LOSER

18. Form: glazing and orientation orientation affects when solar energy is available ORIENTATION ALSO AFFECTS WHEN ENERGY IS ADMITED EAST – SOLAR ENERGY IN THE MORNING - LITTLE IN THE EVENING WEST – LITTLE IN THE MORNING – ENERGY IN THE EVENING SOUTH – SOLAR THROUGHOUT THE DAY Q: CAN ANYONE THINK OF BUILDINGS THAT WOULD SUIT E OR WEST ORIENTATIONS? (E.G. PRIMARY SCHOOL)ORIENTATION ALSO AFFECTS WHEN ENERGY IS ADMITED EAST – SOLAR ENERGY IN THE MORNING - LITTLE IN THE EVENING WEST – LITTLE IN THE MORNING – ENERGY IN THE EVENING SOUTH – SOLAR THROUGHOUT THE DAY Q: CAN ANYONE THINK OF BUILDINGS THAT WOULD SUIT E OR WEST ORIENTATIONS? (E.G. PRIMARY SCHOOL)

19. Form: glazing and orientation so … quantity and orientation of glazing dictates how much and when solar energy is admitted into a building traditional solar buildings have (in temperate climates) significant glazing facing south and little glazing on the north spaces with high glazing areas are subject to significant temperature swings and so are not good performers for comfort often used in conjunction with a ‘buffer space’ IN BUILDINGS WITH A PREDOMINANT HEATING LOAD – WE WANT TO MAXIMISE THE SOLAR GAIN OFTEN DONE USING A CONSERVATORY – TO AVOID PROBLEMS SUCH AS OVERHEATING AND ALSO AS A BASIC ENERGY STORE THERMAL BUFFER SPACE – WARM DURING THE DAY AND EVENING PREVENTS DIRECT SOLAR ACCESS TO THE REST OF THE BUILDING DURING THE MIDDLE OF THE DAY TO AVOID OVERHEATINGIN BUILDINGS WITH A PREDOMINANT HEATING LOAD – WE WANT TO MAXIMISE THE SOLAR GAIN OFTEN DONE USING A CONSERVATORY – TO AVOID PROBLEMS SUCH AS OVERHEATING AND ALSO AS A BASIC ENERGY STORE THERMAL BUFFER SPACE – WARM DURING THE DAY AND EVENING PREVENTS DIRECT SOLAR ACCESS TO THE REST OF THE BUILDING DURING THE MIDDLE OF THE DAY TO AVOID OVERHEATING

20. Form: overheating and shading poorly designed glazing - admitting too much solar radiation at the wrong time of day or period of the year leads to overheating can lead to increased energy consumption – need for mechanical cooling also .. can lead to uncomfortable environment – high daytime temperatures, cool night time temperatures increased heating load in winter POORLY DESIGNED GLAZING CAN BE AN ENERGY PENALTY RATHER THAN BENEFIT – PARTICULARLY IN WARM CLIMATES OR BUILDINGS WITH HIGH INTERNAL HEAT GAINS Q: CAN ANYONE THINK OF BUILDINGS WHICH DO NOT SUIT LARGE GLAZING AREAS? ADMITTING TOO MUCH SOLAR RADIATION CAN LEAD TO HIGH ENERGY CONSUMPTION IF THE BUILDING OVERHEATS AND MECHANICAL COOLING IS REQUIRED ALTERNATIVLEY CAN LEAD TO FRY/FREEZE – TOO HOT IN SUMMER AND TOO COLD IN WINTER – TOO MUCH SOLAR ADMITTED IN SUMMER AND HIGH U-VALUE IN WINTER WORST OF BOTH WORLDS – HIGH SUMMER COOLING LOAD, HIGH WINTER HEATING LOAD! POORLY DESIGNED GLAZING CAN BE AN ENERGY PENALTY RATHER THAN BENEFIT – PARTICULARLY IN WARM CLIMATES OR BUILDINGS WITH HIGH INTERNAL HEAT GAINS Q: CAN ANYONE THINK OF BUILDINGS WHICH DO NOT SUIT LARGE GLAZING AREAS? ADMITTING TOO MUCH SOLAR RADIATION CAN LEAD TO HIGH ENERGY CONSUMPTION IF THE BUILDING OVERHEATS AND MECHANICAL COOLING IS REQUIRED ALTERNATIVLEY CAN LEAD TO FRY/FREEZE – TOO HOT IN SUMMER AND TOO COLD IN WINTER – TOO MUCH SOLAR ADMITTED IN SUMMER AND HIGH U-VALUE IN WINTER WORST OF BOTH WORLDS – HIGH SUMMER COOLING LOAD, HIGH WINTER HEATING LOAD!

21. Form: shading shading can improve the temporal characteristics of glazing WE CAN IMPROVE GLAZINGS CHARACTERISTICS BY ADDING SHADING AND PLACING IT JUDICIOUSLY IN OUR BUILDING SHADING ALTERS THE TEMPORAL CHARACTERISTICS OF GLAZING – I.E. THE TIMING OF WHEN SUN IS ADMITTED Q: CAN ANYONE THINK OF SHADING DEVICES TYPICALLY FOUND IN BUILDINGS?WE CAN IMPROVE GLAZINGS CHARACTERISTICS BY ADDING SHADING AND PLACING IT JUDICIOUSLY IN OUR BUILDING SHADING ALTERS THE TEMPORAL CHARACTERISTICS OF GLAZING – I.E. THE TIMING OF WHEN SUN IS ADMITTED Q: CAN ANYONE THINK OF SHADING DEVICES TYPICALLY FOUND IN BUILDINGS?

22. Form: ventilation the form of the building has a significant impact on the ability to ventilate a building using natural means natural ventilation is achieved by two mechanisms: wind driven pressure and stack effect when considering natural ventilation it is important to remember that the ventilation level is dependent upon wind speed and/or temperature and is therefore variable MOVING ON FROM FORM AND SOLAR ENERGY FORM IS ALSO AN INFLUENCING FACTOR ON NATURAL VENTILATION THIS IS VENTILATION POWERED ONLY BY THE WIND OR INDOOR/OUTDOOR TEMPERATURE DIFFERENCE (STACK EFFECT) OR A COMBINATION OF BOTH IT SHOULD BE KEPT IN MIND THAT AS WE ARE USING NATURAL DRIVING FORCES - NATURAL VENTILATION IS VARIABLEMOVING ON FROM FORM AND SOLAR ENERGY FORM IS ALSO AN INFLUENCING FACTOR ON NATURAL VENTILATION THIS IS VENTILATION POWERED ONLY BY THE WIND OR INDOOR/OUTDOOR TEMPERATURE DIFFERENCE (STACK EFFECT) OR A COMBINATION OF BOTH IT SHOULD BE KEPT IN MIND THAT AS WE ARE USING NATURAL DRIVING FORCES - NATURAL VENTILATION IS VARIABLE

23. Form: wind driven ventilation air flowing over a building gives rise to natural pressure differences creates pressure difference across the building façade – this is the driving force for air flow judicious placement of ventilation opening creates a natural ventilation scheme LETS LOOK FIRST AT WIND DRIVEN VENTILATION THE WIND BLOWING OVER THE SURFACES OF A BUILDING CREATES REGIOS OF HIGH AND LOW PRESSURE PLACING OPENINGS IN HIGH AND LOW PRESSURE REGIONS CREATES THE DRIVING FORCE FOR A FLOW OF AIR. LETS LOOK FIRST AT WIND DRIVEN VENTILATION THE WIND BLOWING OVER THE SURFACES OF A BUILDING CREATES REGIOS OF HIGH AND LOW PRESSURE PLACING OPENINGS IN HIGH AND LOW PRESSURE REGIONS CREATES THE DRIVING FORCE FOR A FLOW OF AIR.

24. Form: wind driven ventilation the available pressure difference between two surfaces of a façade is given by THE EQUATION ABOVE EXPRESSES THE DRIVING FORCE FOR VENTILATION THE PRESSURE DIFFERENCE IS PROPORTIONAL TO THE WIND SPEED SQUARED TO INDUCE A FLOW OF AIR PLACE OPENINGS IN A HIGH AND LOW PRESSURE REGIONTHE EQUATION ABOVE EXPRESSES THE DRIVING FORCE FOR VENTILATION THE PRESSURE DIFFERENCE IS PROPORTIONAL TO THE WIND SPEED SQUARED TO INDUCE A FLOW OF AIR PLACE OPENINGS IN A HIGH AND LOW PRESSURE REGION

25. Form: stack ventilation this is driven by internal and external temperature differences occurs between openings at different heights as with wind pressure ventilation schemes the amount of ventilation is variable STACK VENTILATION MAKES USE OF INTERNAL/EXTERNAL TEMPERATURE DIFFERENCE TO DRIVE A FLOW OF AIR AGAIN THIS WOULD BE A VARIABLE FORM OF VENTILATION THIS REQUIRES OPENINGS AT DIFFERENT HEIGHTSSTACK VENTILATION MAKES USE OF INTERNAL/EXTERNAL TEMPERATURE DIFFERENCE TO DRIVE A FLOW OF AIR AGAIN THIS WOULD BE A VARIABLE FORM OF VENTILATION THIS REQUIRES OPENINGS AT DIFFERENT HEIGHTS

26. Form: stack ventilation stack ventilation calculation: DIVING FORCE IS GIVEN BY THE EQUATION ABOVEDIVING FORCE IS GIVEN BY THE EQUATION ABOVE

27. Form: natural ventilation in low energy buildings the form is often engineered to make best use of stack and/or wind driven ventilation shallow plan (low driving force resistance) atrium (high/low openings + high low pressure) ventilation chimney (high/low openings + high low pressure) WE NEED TO ENGINEER THE FROM OF THE BUILDING IF WE ARE TO MAKE USE OF NATURAL VENTILATION Q: CAN ANYONE THINK OF SITUATIONS WHERE NATURAL VENTILATION WOULD BE INAPPROPRIATE? POLLUTED ENVIRONMENT, TIGHTLY CONTROLLED ENVIRONMENT, ETCWE NEED TO ENGINEER THE FROM OF THE BUILDING IF WE ARE TO MAKE USE OF NATURAL VENTILATION Q: CAN ANYONE THINK OF SITUATIONS WHERE NATURAL VENTILATION WOULD BE INAPPROPRIATE? POLLUTED ENVIRONMENT, TIGHTLY CONTROLLED ENVIRONMENT, ETC

28. Examples: Glasgow solar residences passive solar heating lighthouse building passive solar heating WE HAVE TWO EXAMPLES CLOSE TO THE UNIVERSITY OF BUILDINGS IN GLASGOW MAKING USE OF PASSIVE SOLAR HRATING (TROMBE WALLS)WE HAVE TWO EXAMPLES CLOSE TO THE UNIVERSITY OF BUILDINGS IN GLASGOW MAKING USE OF PASSIVE SOLAR HRATING (TROMBE WALLS)

29. Combining effects finally it is worth pointing out that sustainable form and fabric features are rarely used in isolation – very often combinations are required to achieve the desired effect: thermal mass and night time ventilation mixed mode ventilation – wind driven + stack trombe wall + shading devices VERY OFTEN WE NEED TO COMBINE FORM AND FABRIC FEATURES TO GAIN BEST ADVANTAGEVERY OFTEN WE NEED TO COMBINE FORM AND FABRIC FEATURES TO GAIN BEST ADVANTAGE

30. Review looked at how fabric properties can affect the sustainability of a building fabric: insulation, dynamic performance, thermal mass, condensation, thermal bridges, trombe walls and the impact of form: form: glazing, solar access, passive heating and daylighting, overheating and shading form: air flow, wind pressure, pressure differences, stack effect, temperature differences, ventilation opening RECAP … RECAP …