ALF help

Design help

On the Design pages you enter information about the particular house design and location to perform an ALF analysis on it.

Walls & Windows

Background

On this page you can enter information about the orientations, dimensions and construction types of the external walls. The page also contains the links to the 'Window pages' on which you enter window specifications.

The top of the page shows a check box which will automatically set all the walls to the construction type and insulation level of the first wall.

The 'House Rotation Buttons' let you rotate all the walls with their windows.

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Same Wall Construction Check Box

If you check this box all the walls will automatically be set to the construction type of the first wall. Also the insulation levels of all the walls will be set to the one of the first wall.

Hint:
If most of the walls are of the same construction type it is recommended to check this box. You can then enter this construction type and insulation R-value for the first wall (Wall 'A'). If you the enter dimensions and orientations of other walls the construction and insulation is automatically inserted by the program. At the end or the Same Wall Construction Check Box can be switched off and the walls with different construction types can be modified.

Caution:
Be careful not to click the box once you have entered different constructions and insulation R-values. They will be overwritten if you click the check box.

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House Rotation Buttons

The two 'House rotation buttons', Rotate left. and Rotate right. , allow you to rotate the whole house. This will affect the orientation of the windows and therefore change the solar gains. It will not affect the losses.

Caution:
Rotating the house will rotate the Shading with it. Please make sure that the shading of the windows is updated after the house has been rotated.

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View

Total Window Area

The total window area shows the area of all windows in the currently displayed wall or roof. This area is also shown on the 'Walls & Windows' page.

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Wall Details

Wall Orientation

The orientation of the walls is defined in terms of the eight major compass orientations. The wall orientation affects only the solar gains through the window on the particular wall. It does not affect the building losses.

Wall Length

Enter the external wall length in this box. The wall area is calculated by multiplying the Length by the Height of the wall. The actual dimensions of the wall do not affect the ALF calculation result. Only the net area of each wall is used in the calculations.

If the building includes spaces, which are always unheated and which are generally thermally separated from the rest of the building, such as attached garages or attached garden sheds, these spaces should not be included in the building area. In this case the R-values of the walls separating the building from the unheated attachments can be increased by the R-value of the external walls of the unheated attachments.

Wall Height

Enter the wall height here. The wall height only includes the height of the wall separating the inside and the outside of the heated space. It does not, for example, include the perimeter wall height. The wall area is calculated by multiplying the Length by the Height of the wall.

Wall Net Area

The wall area, which is shown in the box is the total wall area of this wall excluding the window area in this wall. It is calculated by multiplying the length and height of the wall and subtracting the area of all the windows in the wall.

Only the wall area is used in the ALF calculations. The individual length and height of the wall have no effect on the calculation outcome, i.e. a wall which is 3m long and 2m high will have the same ALF results as one which is 2m long and 3m high.

Hint:
Because only the wall area is relevant for the ALF calculation and not the individual dimensions of the wall it is possible to combine walls which have the same orientation and construction type. This may be useful for complicated multi-storey buildings which have more than ten individual walls.

Wall Construction

The drop-down list contains abbreviations of the most common wall construction types. Clicking on one of the abbreviations opens a page with a picture of the selected construction type ('Construction' page). In this page the construction details can be selected.

If the Same Wall Construction Check Box is checked then all except the first wall construction drop down lists are disabled. In order to enable them you have to un-check the Same Wall Construction Check Box.

Hint:
In case you want to bring up the 'Construction' page of the currently selected construction again you have to click once more on the same construction type in the drop-down list.

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Window Details

On these pages you can enter the window/skylight dimensions, the glass type and the frame type for windows in the wall or roof, which is indicated in the header of the page. You can also specify whether and how much the windows/skylights are externally shaded.

The check box on top of the page allows you to automatically select the same glass and frame type for all windows and skylights in the building.

Same Window Type Check Box

If you check this box all the windows and skylights in the whole building will automatically be set to have the same glass and frame type as the first window on the current screen.

Hint:
If most of the windows are of the same type it is recommended to check this box, then to enter the glass and frame type for the first window. When you enter the dimensions and shading of any other windows the program automatically insert the same glass and frame type. When you have entered all the window information the same window type check box can be switched off and the windows with different glass of frame types can be modified.

Caution:
Be careful not to click the box once you have entered different glass and frame types. The glass and frame types will be overwritten if you click the check box.

Window Width

Enter the window width in this box. Include the frame size in the window size because the R-values and SHGC automatically account for that. The actual dimensions of the window do not affect the ALF calculation result. Only the window area is used in the calculations.

Window Height

Enter the window height in this box. Include the frame size in the window size because the R-values and SHGC automatically account for that.

Window Area

The window area is displayed in this cell. It is calculated by multiplying the window width by the window height.

Hint:
Because only the window area is relevant for the ALF calculation and not the individual dimensions of the window it is possible to combine windows on each wall if they have the same glassing and frame type and the 'Shading' is the same. This may be useful for buildings, which have large numbers of windows.

Window construction

Glass Type

Select the glass type in this drop down menu. The 'curtained' glass types assume that good quality thermally lined curtains are used during the evening hours. If curtains are used the R-values are increased by 0.05 m2°C/W.

Frame Type

Select the frame type in this drop-down menu.

Window R-value ('R')

Select the frame type in this drop-down menu.

Solar Heat Gain Coefficient ('SHGC')

The Solar Heat Gain Coefficient (SHGC) depends on the glassing type and the frame, because the amount of the opening, which is covered by the window frame depends on the frame type. Since it describes the solar transmission through the windows, it is not affected by curtains either. (It is assumed that curtains are only drawn during evening hours, i.e. when no or little sunshine occurs.)

Shading

Choose the Shading from the drop down menu for each window. The shading describes the external shading of the window by eaves, plants or other obstacles. Shading of 'a lot' means that the window is shaded for a large portion of the day and only 30% of the available sunlight enters directly or indirectly, shading of 'none' means that the window is not shaded at all.

Shading of 'some' and 'a little' result in 50% and 70% of the available sunlight entering the window respectively.

Caution:
Rotating the house will rotate the shading with it. Please make sure that the shading of the windows is updated after the house has been rotated.

Add a window

Others

Average R-value

The average R-value is the area weighted average R-value of all windows in this wall/roof. It is calculated using the formula:

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Average Shading

The average shading takes account of the SHGCs and the Shading of all windows in this wall/roof. It is calculated using the formula:

Doors

Opaque doors should be treated as double glazed, timber framed windows with 100% Shading if their R-value is not known. If the R-value is known, then the door should be modelled as part of the wall using the 'custom' construction type. This also counts for garage doors. Glazed portions of doors should be treated as windows.

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 Create an ALF account

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Every user needs to create an ALF account. Creating an ALF account will ensure:

  • Confidentiality for your project.
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 Contact and Feedback

Contact us at Branz for further information about the ALF 3.2: Annual Loss Factor.