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7 Preface 9 10 10 10 12 12 12

energy in building Comfort conditions for interior spaces Perception of heat and reaction Most important comfort factors Human reference figures met-value, human power release clo-value, heat transmission resistance of clothing

16 Climate influence 16 External air temperature θe 18 Solar irradiation I 28 Basic mechanisms of heat transfer 28 Exterior environment: Infrared radiation, Convection 30 Interior spaces: Infrared radiation, Heat conduction and convection 32 Boundary layer 36 36 40 42

60 Total balance of opaque building elements 64 Comparison of structures – example

Stationary heat exchange U-value, Temperature profile Loss factor FL Design principles for construction

44 Non-stationary heat exchange 44 Thermal conductance a, Thermal admittance b 46 Periodic excitation: Penetration depth σ, Amount of exchanged energy Q T 50 Dynamic heat storage capacity C 52 Pre-resistance RPr 54 Aperiodic excitation: Time constant τ, Reaction to sudden change 56 Energy transfer through the opaque building envelope 56 Stationary effects: Temperature and irradiation, Mean value of heat flux density 58 Non-stationary effects: Temperature transmittance TT, Radiation based heat transmittance RHT, Isothermal, Adiabatic

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68 Transparent elements 68 Radiation transmission τE , Secondary heat release quotient qi , Total solar energy transmission g, Ug -value, Daylight transmission τV, Spectral selectivity S, Colour rendition index Ra 74 Sun shading 76 Power balance – example 78 80 82 84 84

Air infiltration Required minimum air change rate Assumed maximum air change rate Expected mean air change rate Limiting and target values for the airtightness of the building envelope 85 Design principles 87

integrated energy optimization

88 Dynamic key figures for a room 88 Loss factor K, Radiation receiving area A’RR , Mean radiation transmissivity G, Dynamic heat storage capacity C 90 Gain factor γ, Time constant τ 90 Free-run temperature (FRT) 92 Energy Design Guide (EDG) 92 Optimization of the building envelope in the early planning 94 Energy Design Guide – example 98 Soft HVAC technology 98 Thermally active building elements (TAB) 100 Comfort ventilation 102 Terms of energy management 102 Terms and key data 104 Grey energy – order of magnitude 106 Principles of energy-efficient design

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109

humidity

110 Water vapour and humidity 110 Absolute humidity ν, Water vapour saturation pressure psat , Relative humidity , Dew point temperature θD 111 Vapour pressure curves 112 Water vapour pressure table psat 114 Surface condensation, Mould growth – capillary condensation, Temperature factor fRsi 116 Avoiding mould growth/surface condensation – check-up scheme 118 Water vapour diffusion 118 Water vapour conductivity δ, Diffusion resistance figure μ, Diffusion equivalent air layer s 120 Condensation check-up 128 Amount of condensate check-up

164 Design principles for noise protection 165 Airborne sound insulation of building elements 169

acoustics

170 Running time – Sound reflections 170 Direct sound, First reflections, Diffuse sound 172 Reverberation time T 176 176 178 180

Acoustical design Sound distribution Acoustical optimization of interior spaces Sound reflection

182 Frequency rendition 182 Corrective elements 184 Design principles for acoustical planning 187

daylight

130 Design principles for construction 133

sound

134 Sound dimension 134 Audible frequency range, Sound level L 136 136 138 140 142 144 152

Spread of sound Sound emission level – traffic Noise protection regulation Distance dependency Effect of obstacles Noise protection embankment, Wall Lowering of street level

188 Characteristic values for lighting 188 Light, Luminous flux Φ, Radiation equivalent K, Sensitivity curve of the human eye 190 Luminous intensity I, Luminance L, Illuminance E 196 Daylight transmission factor τV 197 Influence of shadowing 198 Daylight factor DF 200 Determination of the daylight factor 208 Effect and availability of daylight 210 Design principles for good daylighting

154 Airborne and impact sound 154 Determination of noise protection against airborne noise 155 Sensitivity to airborne and impact sound 155 Minimum requirements for internal airborne sound 158 Determination of noise protection against impact sound 159 Minimum requirements for impact sound 160 Nomogram of noise level correction 160 Volume related correction CV 162 Assessed impact sound reduction ΔLW

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215

appendix

258 Subject index 265 Source of figures 267 Authors 288 Imprint

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energy impact

comfort conditions for interior spaces perception of heat and reaction Warm threshold 37 °C Central perception Heat sensors in the brain → reaction if core temperature of the human body rises above 37 °C Universal reaction by sweating to get rid of excess heat through evaporation Cold threshold 34 °C Peripheral perception Cold sensors in the skin → reaction if the skin temperature falls below 34 °C Local reaction by reduction of the blood supply, activation of local muscles (trembling)

most important comfort factors Comfort range of the room temperature 20 °C ≤ θi ≤ 26 °C Temperatures above the comfort range: inactivity, reduced intellectual capability

B Temperature of the surrounding surfaces → less than 3 K below room air temperature → greater differences lead to draught and radiation loss towards cold surfaces Fresh air for breathing and hygiene air change, comfort ventilation* Humidity 30–60% relative humidity recommended best for breathing Moisture* Prevention of mould growth and condensation problems Daylight* provide adequate natural room illumination Sound* Protection against internal and external noise impact Room acoustics* keep the correct reverberation time * see corresponding chapters

The nearer the temperature is to the upper limit of the comfort range, the more sensitive humans are to deviations from the ideal value. Temperatures below the comfort range: adaptation by suitable clothing A Comfort diagram Shows the sensitivity of the human body to surrounding temperatures and its tolerance of discomfort: ± °C

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comfort conditions for interior spaces

10 | 11

A Comfort Diagram Comfort range 20–26 °C, ± °C: sensitivity to differences

B Temperature of surrounding surfaces Discomfort due to radiation asymmetry

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energy in building

B

solar irradiation i [W/m2] With periodic components mean value: I variation (amplitude): ΔI maximum/minimum: I ± ΔI With random component Weather

solar radiation corresponds approximately to the radiation emitted by a black body of 6,000 K. Spectral distribution of the vertical incident solar radiation 4% ultraviolet 56% visible light 40% infrared Power density of the total solar irradiation Imax [ W/m2 ] on the external atmosphere ≈ 1,370 W/m2 on the earth’s surface, depending on the weather Three groups of solar irradiation intensity with different ratios of direct and/or diffuse radiation Attention should be paid to: C Frequency distribution of the radiation intensity to estimate the available power density

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climate influence

B

18 | 19

solar irradiation i [W/m2] on the earth’s surface, depending on the weather

cool, clear blue sky

thick haze

sun breaks through

yellow disc

white disc

sun discernible

stratus

covered sky

Global radiation 1,000 W/m2 500 W/m2 500 W/m2 400 W/m2 300 W/m2 200 W/m2 100 W/m2 50 W/m2 Diffusive percentage 10%

50%

30%

50%

60%

100%

100%

100%

C Frequency distribution Example: Swiss Plateau in winter Time span: November to February, because of stratus Power density I : Intensities above 100 W/m2 2

Intensities below 100 W/m

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100 to 150 h per month

approx. 14–22%

remaining hours of the month

570–620 h

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energy in building

A

transparent elements

total solar energy transmission g

energy transmission

g=

by the glazing, incident radiation Io is divided into reflection, absorption and transmission.

radiation transmission τE τE =

I [–] [no dimension] I0

Part of the incident radiation I o falls directly into the room as radiation

I + Iqi = τE + q i [–] [no dimension] I0

total energy ratio of the incident radiation Io that arrives in a room via a radiation permeable layer Sum of radiation transmission τE and secondary heat release quotient qi

ug -value Ug = 1.5 → 0.4 [W/m2K]

Transmission I consists of: visible light UV ultraviolet and IR infrared radiation

secondary heat release quotient qi qi =

Iqi [–] [no dimension] I0

Part of incident radiation I0 that is absorbed by the glazing and partially transferred to the room by the warm inner surface

The greater the proportion of the glazing in the building envelope and the greater the height of the glazing itself, the lower should be the Ug -value selected, both for energy saving and comfort. The Ug -values influence the surface temperature of the glazing compound inside and thus the boundary layer and the cold air draught. see comfort conditions

daylight transmission τv secondary heat release iqi to interior rooms by infrared radiation convection Strong absorption α by the glazing leads to a high secondary heat release I q: increased static pressure in the glazing and stress on the sealings, reducing the life of the glazing compound. Surface temperatures up to 40 °C in summer are possible: → discomfort near the glazing

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τv [–] [no dimension]

Indicates the ratio of visible light that arrives in the room, wavelengths from 380 nm to 780 nm – daylight sensitivity of the eye Daylight transmission τv should never be lower

than 20% because of the daylight quality in the interior : → sun glass effect see chapter daylighting

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transparent elements

A

68 | 69

energy transmission

IO: Total incident radiation energy (ultraviolet; visible light; infrared) IR: Reected radiation Iqe: Secondary heat release external Iqi: Secondary heat release internal qi: Secondary heat release quotient I: Transmitted radiation intensity τE: Radiation transmission g: Total energy transmission

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integrated energy optimization

B

comfort ventilation Displacement principle Fresh air is fed to the room for hygiene and comfort only. Therefore much less air is transported compared to an air conditioning system. Need per person and hour for standard functions such as living room/office: → 20–30 m3/hP i.e. air change rate n = 0.5–1.5 [h -1]

Vertical distribution Ratio of cross section of air ducts needed per per m2 floor area, for fresh air supply and exhaust air: n·h A ad = A 3600 · v A ad: Air duct cross section [m2] A: Floor area [m2] n: Air change rate [h -1] h: Clear room height [m] v: Air flow speed, 2–4 m/s

No cooling function or only minor: → maximum approx. 10 W/m2

comfort ventilation Example of dimensioning

For passive houses, i.e. very well insulated and airtight houses, the fresh air supply can also provide cooling and heating because very little power density is needed. The inflow of warm air for heating, warmer than the ambient air, however, mixes with the room air, reducing the ventilation efficiency. In other words, one needs more fresh air inflow to attain the same cleaning effect.

Room height, air change rate h=3m n = 2 h -1 Required space for vertical air ducts with air speed v = 2 m/s ratio of areas A ad/A = 0.8‰ → supply and exhaust air

Normally, no volume flow control is necessary (VAV) → on/off according to requirements. Fresh air supply → Horizontal air distribution → Air ducts in the concrete slab, hollow floor etc. → Air outlet at floor level

peripheral, below windows etc. evenly distributed

1.6‰ of floor area with air speed v = 4 m/s ratio of areas A ad/A = 0.4‰ → supply and exhaust air

0.8‰ of floor area In both cases, the space needed for the vertical air ducts is small because of the small air volume needed.

Free cross section of air outlet needed depends on air change rate and room height. = 1.0 h -1 and room For an air change rate n ~ ~ height = 3.0 m → approx. 3.3–5.5‰ of the floor area Outlet flow speed: v ≤ 0.3–0.5 m/s Exhaust air near ceiling, along corridor, central collection via baths, kitchen, toilet

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soft hvac technology

B

100 | 101

comfort ventilation based on the displacement principle

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humidity

avoiding mould growth/surface condensation Check-up scheme Water vapour curves

θsi − θe θi − θe

known: θi , θe , φ

θsi

fRsi =

sought: φ

θsi

θsi = θe + fRsi · (θi − θe )

Example: θi = 20 °C, θe = -4 °C, φ = 50%

θsi = 12.5 °C

φ = 71%

θsi = 18.04 °C

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fRsi =

12.5 – (-4) 16.5 = = 0.6875 24 20 – (-4)

θsi = -8 + 0.93 · (20 – (-8)) = 18.04 °C

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water vapour and humidity

116 | 117

Temperature factor curve (exact)

fRsi

sought: U

fRsi

known: U, θe , θi

fRsi = 0.6875

U-value = 1.1 W/m2K

fRsi = 0.93

U = 0.2 W/m2K, θi = 20 °C, θe = -8 °C

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sound

distance dependency Noise level L(r) as function of distance r from source Point source

Free space C Half space, on a plane

Linear source

L(r)= L0 − 20 · log (r) − 11 dB L(r)= L0 − 20 · log (r) − 8 dB

L(r)= L0 − 10 · log (r) − 5 dB

Quarter space, in front of a house, embankment

L(r)= L0 − 20 · log (r) − 5 dB

L(r)= L0 − 10 · log (r) − 2 dB

Eighth space, in a corner

L(r)= L0 − 20 · log (r) − 2 dB

Doubling of distance

−6 dB = 20 · log (2)

−3 dB =10 · log (2)

L0 = Source level at 1 m from source = sound power level Note log (u · v) = log u + log v log

u = log u – log v v

log

1 = – log v v

log (ur) = r · log u x = 10 logx Note A heavily frequented road has to be considered as a linear source. The noise decreases less quickly with increasing distance from the noise source, see doubling of distance.

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spread of sound

140 | 141

C Decrease of sound level ΔL in half space known: Noise source Data at first measuring point Distance of new measuring point from noise source

Point source: ΔL = L1 – L2 = 20 · log

Linear source: ΔL = 10 · log

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r2 r1

r2 r1

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sound

E

noise protection embankment Reduction of trafďŹ c noise on a double-lane road

Reduction of the equivalent permanent noise level through a noise protection embankment by a double-lane road. Parameter: Height of embankment h [m]

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spread of sound

E

144 | 145

noise protection embankment Reduction of trafďŹ c noise on a double-lane road r = 25 m

r = 50 m

r = 100 m

r = 200 m

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acoustics

running time – sound reflections A

running time – sound reflections Determining the dimensions of performance spaces through the acceptable differences in sound path lengths.

direct sound on a direct path through the air

first reflections on indirect paths by reflections from walls or ceiling Time sequence of first reflections Within a period of more than 20 milliseconds [ms], and up to 80–100 ms, the human ear adds the first reflections into a single sound impression, which it perceives as direct sound. B

Δs [m] Direct sound – first reflections Δs = v · Δt [m] Δs: Path difference [m] v: Sound speed [m/s] Δt: Time difference [m/s]

path differences

diffuse sound on even more indirect paths through several successive reflections from different surfaces Reverberation time T [s] The time it takes for a diffuse sound to die away Short enough: so that sound continuation is not superimposed Not too short: otherwise there will be no impression of space

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running time – sound reflections

A

running time – sound reflections

B

path differences Δs [m] Direct sound – first reflections Δt = 20 ms v = 340 m/s → speed of sound (in air) 340 · 0.02 = 6.8 m Sound detour

Delay

Effect

0.3–7 m

0.8–20 ms

Early interferences should be suppressed, as they colour the sound unpleasantly

7–17 m

20–50 ms

Range for speech

7–27 m

20–80 ms

Range for music

7–34 m

20–100 ms

Maximum range of accumulation by the ear

> 34 m

> 100 ms

Reflexions are perceived as disturbing echos

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170 | 171

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daylight

luminous intensity i [cd=lm/sr] ( luminosity ) I=

Φ [cd = lm/sr] Ω

Amount of light emitted, for solid angle Ω in candelas [cd] Sphere: 4 π Hemisphere: 2 π A = 2 [sr] (steradians) Solid angle Ω ~ r A: Surface of the cap of the sphere [m2] r: Radius of the sphere [m]

secondary light source l [cd/m2 =lm/m2sr] E·R L= [cd/m2 = lm/m2sr] π

Any illuminated surface with diffuse reflectivity R represents a secondary light source with a luminance L: indirect illumination/glare e.g. matt white writing paper (R = 0.8) in full sun

luminance l [cd/m2 = lm/m2sr] L=

Φ I = [cd/m2 = lm/m2sr] A A·Ω

A: Luminous surface [m2] Ω: Solid angle [sr]

Differences in luminance are relevant for visual perception

illuminance e [lx=lm/m2] E=

Φ

A

[lx = lm/m2]

A: Illuminated area [m2] Effect on the illuminated object. Luminous flux in relation to the size of the illuminated surface in lux [lx].

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characteristic values for lighting

190 | 191

characteristic values of lighting – interrelationships

Example: Luminous flux Φ 1,000 lm Luminous intensity I I = 1,000 lm: 1.7 sr = 588.2 lm/sr = 588.2 cd Luminance L of a lamp L = 588.2 cd: 0.01 m2 = 58,850 cd/m2 Illuminance E E = 1,000 lm: 2 m2 = 500 lx = 500 lm/m2 Luminance L of paper (secondary light source) L = 500 lx · 0.8/π = 127.3 cd/m2 = 127.3 lm/m2sr

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appendix

Conversion of Imperial units

symbols and units

Length

Factors and their denominations 10 -15

f

femto

10 -12

p

pico

10 -9

n

nano

10 -6

µ

micro

10 -3

m

milli

103

k

kilo

106

M

mega

109

G

giga

12

T

tera

15

10

P

peta

1018

E

exa

10

inch

1 in

= 2.54 cm

foot

1 ft

= 12 in = 0.3048 m

yard

1 yd

= 3 ft = 0.9144 m

mile

1 mile = 1,760 yd = 1,609 m

Area

square foot 1 ft2

= 0.0929 m2

Mass

ounce

1 oz

= 28.3495 g

pound

1 lb

= 16 oz = 0.4536 kg

Energy

Btu, British 1 Btu = 1.05506 kJ thermal unit

Power

Btu/h

Thermal Btu/h · ft conductivity

Btu/h · ft = 1.7306 W/mK

Heat flux density

Btu/h · ft2

1 Btu/h · ft2 = 3.155 W/m2

Heat transfer coefficient

Btu/h · ft2 · F

Btu/h · ft2 · F = 5.674 W/m2K

velocity

fpm, feet per minute

ft/min = 0.00508 m/s

air flow

cfm, cubic feet per minute

1 ft3/min = 0.4719 lt/s

moisture

gr/lb, grain per pound

gr/lb = 0.143 g/kg

pressure

lb/ ft2, lb/ ft2 pound per = 47.9 Pa square foot

Temperature Fahrenheit

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1 Btu/h = 0.293 W

°F = 1.8 · °C + 32 °C = (°F – 32) · 5/9

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symbols and units

218 | 219

Work, energy, heat quantity J (= N x m)

MJ

kWh

kcal

Btu

J (= N x m)

1

10 -6

0.278 x 10 -6

0.239 x 10 -3

0.9478134 x 10 -3

MJ

106

1

0.278

238.663

0.9478134 x 103

6

kWh

3.6 x 10

3.6

1

862

3,412.128

kcal

4.19 x 103

4.19 x 10 -3

1.16 x 10 -3

1

3.968305

Btu

1.05506 x 103

1.00506 x 10 -3

0.0002930722

0.2519968

1

Power, heat ow W (= J/s)

kW

PS

kcal/h

Btu/h

W (= J/s)

1

10 -3

1.36 x 10 -3

0.860

3.413

kW

103

1

1.36

860

3.413.103

PS

0.735 x 103

0.735

1

632

0.398.10 -3

-3

kcal/h

1.16

1.16 x 10

Btu/h

0.293

10 -3 x 0.293

1.5 x 10

-3

2.508.103

1

0.253

3.959

1

Water vapour conductivity

mg/mhPa

mg/mhPa

kg/msPa

g/mhTorr

1

0.278 x 10 -9

0.133

kg/msPa

7.5

2.08 x 10

g/mhTorr

3.6 x 109

1

-9

1 0.48 x 109

Pressure, mechanical tension Pa = N/m2 = kg/ms2

bar

mm WS (= 10 -4at)

Torr (mm Hg)

Pa = N/m2 = kg/ms2

1

10 -5

0.102

750 x 10 -5

bar

105

1

0.102 x 105

750

1

736 x 104

13.6

1

-4

-5

mm WS (= 10 at)

9.81

9.81 x 10

Torr (mm Hg)

133

133 x 10 -5

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PINPOINT. Key Facts + Figures for Sustainable Building