A window tool which is part of the REALcosting software is now available separately for PHPP. This can save you hours! It is available in 2 versions, a basic version (which is simpler to use and calculates approximate d reveals) and an exact version for PHPP certification. Please ask for a free trial.

Both are suitable for PC computers only, not Apple Mac, using Microsoft Excel 2010 onwards with PHPP versions 9.1 to 9.6, 8.5, 2007 and REALcosting spreadsheets (there is also a special button for it within REALcosting, whether or not you have the window tool). If there are any other versions you would like it for, please let me know. The window tool is launched from the quick access toolbar.

The software requires macros to be enabled to run. ‘Installation’ is only a matter of adding it to the quick access toolbar, which takes 2 minutes, it is uninstalled a similar way.
The basic version is £40 and the certification version is £55. Please contact tim@optimalretrofit.co.uk for more information and to purchase. It is sent by email to you.

Basic Version

It enters the dimensions of each pane in the window, the 1’s and 0’s and it calculates the average d reveal, details of that calculation is lower down the page. In the video I add a blank row between windows to show it can be done, you don’t have to do that. The window tool also adds a number or letter to the end of the name for each pane. So for example below the name of the window entered was W1, W2 etc, the software added the ‘a’ and ‘b’ for each pane.

Everything shown below is entered by the software. You don’t have to close and re-open the tool between windows, you can use the ‘up’ and ‘down’ buttons to re-position your starting row, you can even overwrite an existing window entry.

Certification Version

Why Frames Thicknesses Vary
The window tool will calculate the correct d reveal using complex variations in frame thickness.
Frame thickness around windows varies, there are several reasons:
1) Opening window frames are wider than fixed frames.
2) Mullion widths are narrower than butting external frame edges next to each other. Some windows have a mullion on one side, some on both.
3) Mullion widths vary according to what type of window (fixed or opening) is on each side.


Frame Information
The window tool reads your frame information from the components tab, shows it on the screen and uses it in the calculations. This means you need to enter them first.

An example of the list of frame types is below. You might need 3 versions of a fixed window and 3 versions of opening window (could be more or fewer depending on your windows).

Pane 1 in the diagram above is type 5, opening with one half mullion. Pane 2 is type 3, fixed with one half mullion.

Half mullions could be on the left or right, but since these mirror images give the same result in calculations only one of them is listed.

The full mullion width is shared between the two windows either side.

Where fixed half mullion are used (types 2 and 3 in the table above) just the manufacturers mullion width/2, = 0.101/2 = 0.051m

The correct mullion width to use in that calculation should be where there are fixed windows on BOTH sides of the mullion.

Allowance is made in below for the extra width of mullions for opening windows.

When an opening half mullion is used we do not want to have to redefine the width of a fixed half mullion, so that stays the same. For types 5 and 6:
full mullion width = fixed half mullion + opening half mullion

Therefore use
opening half mullion = full mullion width – fixed half mullion

In other words, the opening half mullion width to use is just the extra than half a fixed mullion.
This will then give the correct result when the two half mullions are put together, unless a post is needed.
Where there are 2 opening windows side by side there will be a post as well, which makes the frame even wider, the 210 width above.

Explanation of the Calculation
A typical image used in the window tool has a very simple diagram shown to the right:

Full details of what you should measure to are shown below.
dreveal1 is not the thickness of the frame, it is the distance to the shading edge which is often less in Passivhaus buildings.

For example supposing a=1.5m, c=0.4m, frame1L =0.12m, frame1R=0.090m and cover is 0.030m
dreveal1 = frame1L – coverL
dreveal1 = 0.120-0.030 = 0.090m

dreveal2= frame1R + (a – c) – coverR
dreveal2= 0.090 + 1.5 – 0.4 – 0.030 = 1.16m

Average dreveal= (0.090 + 1.160)/2 =0.625m

The average d reveal is calculated for each pane individually. Where there is SHADING BY THE BUILDING you will need to adjust the d reveal.
Figures are filled in to the sheet starting from the row of the current active cell, the faint grey numbers on the window image indicate the row each window part will be written to, starting at ‘1’ for the active cell.

Using the Tool
Steps are given in red over below:

Also note that:
● you can add several windows or overwrite windows without closing the tool, just use the up and down buttons to position your starting line.
● if there is SHADING BY THE BUILDING, for example by an ‘L’ shaped or ‘U’ shaped building, then the d reveal will be different. In that case the average d reveal must be obtained manually from measurements from drawings.

If you are having the building certified it is recommended you check the certifier is happy with the way the d reveal is calculated. Every effort has been made to ensure the figures the tool gives are correct, however no liability is accepted for inaccuracies. For support please call Tim Martel 07531 288 147.