Hvordan oppnå optimale lysforhold i lavenergi bygg?

Transkript

1 Hvordan oppnå optimale lysforhold i lavenergi bygg? LOW-ENERGY HOUSE, BACK TO THE ÅRESTUE, a thought experiment about the low-energy architecture Barbara Matusiak Norwegian University of Science and Technology NTNU, Norway

2 What is a though experiment? Process whereby one considers imaginary situations in order to develop theories as well as help to understand why things are as they are. It is an a priori process, since experiments are performed in the imagination. THE QUESTION: What consequences emerge when a standard of extreme energy efficiency is applied to the cold and unforgiving Norwegian climate.

3 ASSUMPTIONS Building for a modern person who stay 90% of time indoors Comfortable indoor conditions 21º-23º, with an airflow velocity of 0.15 m/s High functional and aesthetic standard Need for outside view Adequate lighting conditions Technical equipment, etc... ANNALYSIS Energy is needed to maintain a stable indoor temperature. It depends on the size of the envelope, its ability to insulate, and the disparity in the temperatures indoor-outdoor. better insulated walls, floors and roofs means usually thicker

4 But what about windows? Windows are necessary for reasons other than protection from the outdoor climate. They provide visual contact with the outside environment, facilitating numerous human needs, namely that of information about the place, time, and weather, and the presence of other creatures, notably people. The highest U-values permitted by Norwegian building code Internal temperature and the U-value (W/m 2 K) Envelope elements: T>20ºC 15º<T<20º 15º<T<20º 15º<T<20º Outside walls 0,22 0,28 0,40 0,60 Roof, floor on the ground 0,15 Windows 0,20 and skylights 0,30 in Norway 0,60 should have maximum insulation Floor towards not heated 0,30 ability 0,40 as well as 0,50 minimum area 0,60 that room enables visual contact with the Windows 1,60 outside 2,00 environment 2,50 and secures 3,00 a daylighting level necessary for Glazed walls and roofs 2,00 maintaining 2,00 health 3,00 and wellbeing 3,00 of occupants.

5 Toward reducing the energy requirements for heating and cooling 1. minimum volume per person 2. compact building body 3. well-insulated envelope - thick? walls and roofs - smartly designed windows

6 1. MINIMUM VOLUME PER PERSON Function/activity Economy Construction Status etc.

7 2. A COMPACT BODY Compactness can be defined as the relationship of volume to the area of the exterior envelope. Compactness depends directly on the volume. For example, with an increase in radius from 1 to 10 the compactness of a sphere grows from to Spherical form:

8 Pantheon 2. A COMPACT BODY

9 2. A COMPACT BODY Cubical form The cube is the most compact rectangular three dimensional form. The area of the envelope relative to the area of the floors of all parallelogram forms is at a minimum in a cube. A cube has a 24% greater surface area to that of a sphere with equal volume and a 15% greater surface area of that of a transformed spherical form with the same volume. 10% larger surface area than the transformed sphere

10 2. A COMPACT BODY ALT1: Width: 17m, Height: 2,7m, H(v)=1,7m H(b)=0,9m ALT2: Width: 24m, Height: 3,0m, H(v)=2,4m H(b)=0,6m ALT3: Width: 33m, Height: 3,3m, H(v) 3,3m H(b)=0,6m

11 2. A COMPACT BODY ALT1: Width: 17m, Height: 2,7m H(v)=1,7m H(b)=0,9m ALT2: Width: 24m, Height: 3,0m H(v)=2,4m H(b)=0,6m ALT3: Width: 33m, Height: 3,3m H(v) 3,3m H(b)=0,6m Fixed office work areas should not be more than 3-4 m away from the window!

12 Kunstgalleri i Berlin 2. Limits of compactness?

13 3. WELL-INSULATED ENVELOPES Room: 4*4*3m, walls insulated with mineral wool 15cm Window: 2-layer clear glass, LT=80% Alt. A DF(av)=2,6% Let s increase the thickness of the thermal ins. in walls to 40cm Alt. B DF(av)=2,0% Let s use very well-insulated 3-layers glazing, LT=71% Alt. C DF(av)=1,8% Let s use glazing with sun shielding to reduce overheating, LT=44% (Suncool 50/25) Alt. D DF(av)=1,07%

14 3. WELL-INSULATED ENVELOPES Alternativ A Alternativ B Alternativ D Illuminance (lux) at a horizontal plane 80 cm over the floor. The outside illuminance is lux.

15 3. WELL-INSULATED ENVELOPES Can the low LT of sun shielding glazing be offset with a larger window area? Yes, Suncool 50/25 window must be increased to 2,08 x 2,08m Does the Suncool 50/25 window contributes more to sparse energy use than a smaller window having LT=80%? If U(window)=1,6W/m 2 K and U(wall)=0,12W/m 2 K, the weighted value for 2,08 x 2,08m fragment of the wall is: 0,89 W/m 2 K 0,7 W/m 2 K Suncool 50/25 3-layer.

16 Conclusions from the though experiment? The experiment exposes the latent wisdom buried here in the traditional well-adjusted architecture of the årestue, an anonymous architecture that emerged in an age when people could not afford to waste resources. A modern version of the Norwegian årestue would be built using modern materials and advanced technology, but the form would be surprisingly similar.

17 Where does this extreme focus on energy efficiency lead us? minimizing the volume per person maximizing compactness: maximizing the volume to the extent that it allows outdoor visual contact optimizing the shape of the building maximizing the envelope's insulating ability maximizing wall, roof and floor thickness optimizing window shape: low U-value, limited size maximizing light revenue from daylighting openings How?

18 DF Daylighting design? Komponentene av DF Dagslysfaktoren er sammensatt av tre komponenter: Himmelkomponent (HK), Utereflektert komponent (URK) Innereflektert komponent (IRK) DF = HK + URK + IRK HK URK IRK Avstand fra vindusvegg

19 Maksimal skjermingsvinkel REFERANSELINJE FOR DAGSLYS- BEREGNING 25 O 2 m SKJERMENDE BYGNING

20 Lysåpningens størrelse

21 Lysåpningens størrelse Bauhaus, Dessau, Germany, Architect: Walter Gropius

22 Lysåpningens form og plassering

23 Lysåpningens form og plassering Jødisk Museum i Berlin, Daniel Libeskind, 1999

24 Lysåpningens utforming Dagslysfaktor i to rom: likt glassareal, forskjellig vindusinnsetning

25 Lysåpningens utforming

26 Vinduers lys- og isolasjons egenskaper Funksjon Type vindu Lystransmisjon U senter [%] [W/m2K] Energiglass 4-15-e4 77 1,6 4-15g-e4 77 1, g-e4 69 1,2 4e e4 66 1,1 4e-12g-4-12g-e4 66 0,8 Solavskj. Blåfarget ,2-2,8 Bronsjefarget ,2-2,8 Grønnfarget ,2-2,8

27 Dagslysfaktor, DF [%] Reduksjon av lystransmisjon DF reduseres som følge av lavere lystransmisjon gjennom glassene Lystransmisjon 80% 60% 40% 20% Romdybde, l [m] 0

28 Glass og lystransmisjon glass 2 glass 3 glass Refleksjon av ett lag glass: 8% Absorpsjon: 1-3% (tykkelse) TRANSMISJONSFAKTOR [%] INNFALLSVINKEL [ o ] Transmisjonsfaktor for lys ved varierende innfallsvinkel

29 Lystransmisjon

30 Himmelsektordiagram Glassets lystransmisjon varierer som funksjon av lysets innfallsvinkel. Og CIE-overskyet himmel har tre ganger så høy luminans i senit som i horisonten. Følgelig kommer mest lys fra himmelsektoren ved ca 40 o. 4,0% 1% 13,6% 4% 8% 19,6% 13% 20,0% 20% 16,5% 20% 12,7% 17% 8,2% 13% 4,2% 4% 1,2% Vertikalsnitt gjennom 2-lags glass. Figuren illustrerer hvor stor prosentandel av himmellys vinduet slipper i gjennom fra ulike himmelsektorer. Hver sektor er 10 grader.

31 Balkong? Takutstikk? Balkongutstikk reduserer dagslysnivået i nedenforliggende rom DF [%] ,0 2,0 3,0 10 1,0 5 2,0 3,0

32 Takutstikk Det nye regjeringskvartalet i Berlin; bibliotek.

33 Lyshylle Radiance studier klar himmel med sol Med lyshylle, diffuserende overflate Uten lyshylle Med lyshylle, speilende overflate

34 Glassets helning Vertikalt glass DF mid =20*A lys /A golv DF min =10*A lys /A golv A lys vinduets lysareal [m 2 ] A golv totalt golvareal [m 2 ]

35 Skråstilt glass: DF mid =35*A lys /A golv

36 Glassets helning Vertikalt glass: DF mid =20*A lys /A golv Skråstilt glass: DF mid =35*A lys /A golv Horisontalt glass: DF mid =50*A lys /A golv

37 Overlyset: helning og plassering Kiasma, Helsinki, arkitekt: Steven Hall

38 Kiasma, Helsinki, arkitekt: Steven Hall

39 Overlyset: helning og plassering Trondheim Kunstmuseum, tegnet av prof. Petter Daniel Hoftun 1930, utvidelse fra 1987 tegnet av prof. Ola Steen. Overlyset: helning og plassering

40 Overlyset med speil Enebolig Steinåsen, tegnet av Barbara Matusiak, 2007.

41 The light cone idea Per Knutsen arkitekter, Trondheim

42 The light cone idea

43 The light cone idea Reflector 1 Reflector 2 Reflector 3

44 TRANSLUCENT FAÇADES in Deichman library Lund Hagem and Atelier Oslo, were selected as a winners of the architectural competition The illustration of the new building of the Deichman Library from the competition presentation.

45 Solar glare from translucent facades Scenario 1: 1. The participants were asked how glary the façade was intolerable glare disturbing noticeable barely perceptive 2. They were asked to read test charts at the mobile phone (three times). The reading speed was measured 3. They were also asked how difficult the reading conditions were impossible to read hard to read uncomfortable to read no difficulty Scenario 2 as scenario 1, but 1/3 of the façade was open for outside view Scenario 3 as scenario 2, but subjects could choose the position of the mobile phone screen Scenario 1 Scenario 2 and 3

46 Hvordan oppnå optimale lysforhold? Unngå unødvendig utvendig skjerming: - høye nabo-bygninger/terreng/trær - Takutstikk, balkonger, pilarer etc. og - fastmonterte solskjermingselementer Sørge for: optimal dagslys design: utsyn samt belysningsstyrke- og luminansfordeling må vurderes sammen plassering av dagslysåpninger (vegger og tak) helning av glass (om mulig) høy lystransmisjon av glass kontroll av sollys/blending (om nødvendig) med et system som muliggjør vis. kom. med ute og maksimal dagslysinnstråling ved overskyet himmel evnt. kontrollert redirigering av sollys