BUILDING DESCRIPTION

The research studies a modular SIP construction unit, one storey dwelling with the overall floor area is 45m², 11.85 m length and 3.80 m width (referred later as ErgoHome building unit, EH). Steel feet are at 1.25 m height, the overall height: 3.5m and plan:

11.85 x 3.88 m. The space volume is of 132 m³ with the roof slope (no loft cavity) of 15°, containing five thermal zones and designed regarding their usage purposes as five different rooms: living space, bedroom, office, bathroom and entrance hall. Building dimensions are given in the plan and front section of the building unit as shown in Figure 4-2 and 4-3. All windows are at 0.8m height level except the fixed window W3 is at 0.96m.

The higher glazing area is on short sided wall that faces south east and north west compared to the building front and back facades on south west and north east orientation. In fact, the window-to-wall ratio (WWR: net glazing area to gross exterior wall area) on short sided wall is 0.24 and 0.18 against its value on long sided wall of 0.04 and 0.08.

The test unit does not have self -shading as it has a very simple shape (rectangle) and not equipped with any overhang. Trickle vents of 40 cm² are included in small and large window types as required for new buildings in order to provide a controllable ventilation source.

Figure 4-2: Side view of ErgoHome test building

Figure 4-3: Plan ErgoHome test building

4.2.1 Constructional information

SIP system composed of Oriented Strand Boards, “multi-layered board mainly made from strands of wood together with a binder”, OSB/3 (which are classified as load bearing boards for use in humid conditions) (BSI, 2006) facings with a rigid insulation core. It is manufactured by injecting a precise blend of chemical polyurethane foam (PU) under high pressure between the OSB faces. This creates autohesive bonds the OSB and the foam core together as the chemical reaction occurs, resulting in superior bond strength compared to lamination techniques, and guarantees a continuous bond across the entire surface area of the panel (SIPCO, 2009). There is slightly difference in SIP composition between wall, roof and floor structures (see Table 4.1).

Table 4-1: Constructional information Building

element/

Details of layers in external – internal order

External wall Cedar timber (6 -22 mm); ventilated air cavity with batten support (25 mm); OSB/3 (11mm); polyurethane foam (103 mm); OSB/3 (11mm); unventilated air cavity with batten support (12.5 mm);

gypsum paper-faced board (12.5 mm)

Ground floor OSB/3 (11 mm); polyurethane foam (103 mm); OSB/3 (11mm);

polystyrene (PS) (18 mm); black PS (30 mm) with PS balls (3mm) thermally modified; oak radial (oak spruce: 11 mm and oak: 4 mm) Pitched roof (15°) Aluminium corrugated with air ventilated; building membrane;

OSB/3 (15mm); polyurethane foam (120 mm); OSB/3 (15mm);

plasterboard (12.5 mm)

Internal partition Plasterboard (12.5 mm); rock wool sound insulation (63 mm) with timber studs; plasterboard (12.5 mm);

Window Double glazed: outside pane: clear float and inside pane: “iplus DK” (low e-coating), argon filled (93%) whilst ignoring frame effect

The test unit utilises windows of VELFAC 200 system. They are to be a unitised composite aluminium/wood system (VELFAC, 2009). There is no shading device and trickle ventilator of 40 cm² each are equipped in small and large window types so as to provide controllable ventilation source.

Table 4-2: Information of glazing elements

Windows Descriptions

Glass Element details Light Solar heat U-value, W/m²K

4|16|: 4 Outside pane: float Light transmittance LT = 0.8 Solar heat factor: SG = 0.62 1.11 Calculation method

respect BS EN ISO 673 and 410 (BSI, 1998 and 2007b)

Cavity is filled with argon (filling degree: 93% )

Light reflectance (both pane)

= 12%

Transmittance = 54%;

Reflectance = 27%;

Absorptance = 11% / 8%

Inside pane: iplus DK, which is double silver coating at inner side

Frame/sash - Depth of unit 124 mm from this 90 mm frame

- The external aluminium sash must be polyester powder-coated in compliance with BS 6496, BS 6497, GSB and DIN 50939, in RAL colour to gloss level 77% and a primary coating thickness of between 60-120 µm.

Type Quantities Dimension (WxH), mm Sash area, m² Glazed area, m² U-value , W/m²K

Large window 4 886 x 1023 0.207 0.71 1.71

Small window 10 623 x 1023 0.18 0.47 1.83

Fixed window 2 373 x 773 0.123 0.18 2.17

French patio door 4 1173 x 1983 0.686 1.66 1.82

Entrance door 2 914 x 2013 1.84 0.09 0.92

4.2.2 Thermal properties of the fabric of building envelope

With the building constructional information given in the previous section, the thermal properties of the building envelop were determined thus enabled development of computer simulation modelling. Summarised calculated parameters are given in Table 4-3 (next page), and detailed calculations can be found in Appendix B Section B.1.1 and Section B.1.2.

Several passive design principles and techniques employed in the test building to achieve energy efficient perspectives are listed below:

- SIPs are the main construction of the test building. Polyurethane is used as the insulation layer and possesses higher R-value than current insulation materials (EPS or XPS) and being close cell foam helps reduce condensation risk. For example, a 114mm thick of the insulation layer, R-value of PUR SIPs can reach up to 4.58 m²K/W (U-value

= 0.21 W/m²K) while XPS SIPs possess lower R-value of 3.34 m²K/W (e.g. U-value = 0.30 W/m²K) and EPS SIPs provides lowest R-value among 3 types with R-value of 2.82m²K/W (e.g. U-value = 0.36 W/m²K) (The Murus Company Inc, 2009).

- Opening area of test unit is designed in accordance with recommendations for natural ventilation requirements. It is stated that ventilation openings with total area of at least 1/20 of the floor area of the space are (DCLG, 2010b).Hence, window area = 10.96 m² > 1/20*44.96 = 2.25 m². Additionally, trickle ventilator of 40 cm² each are equipped on a range of large and small windows to satisfy the requirement of background ventilation (DCLG, 2010b).

- The test building employs high energy efficient windows with improved U-values down to between 1.71 and 1.82 W/m²K (See Appendix B Section B.1.1.1.6). In order to achieve this, the window design is based on minimising the frame/glass ratio.

Double glazing with low e-coating on internal pane as well as argon filled cavity with warm-edge spacer has been used (VELFAC, 2009).

- Solar panel on south facing slope roof and mechanical heat recovery ventilation system are available for further design development but were not included in the research project regarding its scope of considering building thermal performance alone.

Table 4-3: Summary of calculated thermal parameters for building components Element Construction information Transmittanc

e Admittance Decrement factor Surface factor

External – internal order U, W/m²K Y, W/m²K ω, h f, - ø, h F, - ψ, h External

wall

Cedar timber (6 - 22 mm); Ventilated air cavity of 25mm; SIP 125: OSB/3- PU-OSB/3 (11-103-11mm); Unventilated air cavity with batten support (12.5 mm); Gypsum paper-faced board (12.5 mm).

0.24 0.92 4.38 0.91 -2.90 0.96 -0.44

Pitched roof (15°)

Aluminium corrugated with air ventilated space and building membrane; SIP 150:

OSB/3 - PU - OSB/3 (15-120-15mm);

Plasterboard (12.5 mm).

0.22 1.20 4.60 0.94 -3.05 0.96 -0.58

Ground floor

SIP 150: OSB/3 - PU - OSB/3 (11-128-11 mm); Polystyrene (PS) (18 mm); Black PS (30 mm); Oak spruce (11 mm).

0.16 0.95 4.27 0.79 -6.45 0.95 -3.61

Internal partition

Plasterboard (12.5mm), rock wool insulation

(75mm), plasterboard (12.5mm) 0.49 0.79 7.64 1 -1.06 0.92 -0.85

Window

Glazing (4|16|: 4) Outside pane: clear float;

Cavity is filled with argon (filling degree:

93%); Inside pane: iplus DK, which is double silver coating at the inner side.

- Windows with different percentage of frame fraction f

1.1 (glazing

only); 1.26 1.79 1 -0.36 0.86 -0.33