Knowing well the weather station data that Revit will use for calculating the thermal demand is the amount, as it allows us modify it and check that come by default.

In the following video is this consultation and edition:


The dialogue “location” located on the “manage” we will serve to geographically locate the project. When defining this location we will have 2 options:


1. – Internet mapping service

2. – Default city list


We must remember that the Internet Mapping service option should be used for the conceptual design, while Default City List is the right choice for a thermal load calculation, as we ensure that meteorological data are part of the World Meteorological Organization.

Building infiltration class

In the calculation of thermal loads Revit MEP offers us the possibility of regulating the flow due to infiltration. This rate with respect is regulated in three steps:


loose = 1,38 m³/h x m² – (0,076 CFM/Sq x ft)

medium = 0,69 m³/h x m² – (0,038 CFM/Sq x ft)

tight = 0,34 m³/h x m² – (0,019 CFM/Sq x ft)

none = 0 m³/h x m² – (0 CFM/Sq x ft)


It is important to remember that the surface on which Revit calculates wall surface is in contact with the outside. Here’s a video showing the comments:

Systemair Plug-in for AHU selection

Few manufacturers have developed their product catalogs for Revi MEP and in this post we talk about Systemair. Unlike others they didn’t send a huge full of families arranged at their discretion but a selection software for the AHU units and a plug-in for Revit that imports the file generated, as a family, in our project.

In the version I tested the families exported only had information about the  air connectors although the families parameters are not yet linked to the connector parameters.

The hydraulic parameters are not yet included, honestly do not understand why you skipped. As for the electrical parameters, as Systemair, not included by the installation of the equipment in situ are not typical configurations but still electricity consumption unchanged.

Manage the selection program has some difficulty and we leave Systemair experts who choose the conditioner that best suits our needs and send together with the financial offer SystemaAirCad file. For now this workflow is that we should lower.

Install the software

From their official website we download and install the software SystemairCAD selection, we will find in the “Global / Support / Software tools / SystemairCAD”. On the same page we have instructions on installing the plug-in for Autodesk Revit


SystemairCAD is able to export a DMR file of a 3D CAD model.

A small plug-in have to be installed, to import the 3D model to Autodesk Revit.

The import plug-in together with instructions how to install it can be downloaded via the following link:

The purpose of the connection is to add Systemair air handling units selected with SystemairCAD into MagiCAD for Revit or Revit project and drawing.


Import an AHU

The plug-in offers two options for importing an air conditioner but we are going to focus only on the second, importing a file. “dmr” exported from SystemairCAD.

On the same page to download the plug-in found the Systemair Revit Plugin – Users Guide.pdf with details about the different ways available to import.


Building construction

Possibly the most important parameter in the calculation time of the thermal loads, and that from this are the thermal properties to assign each of the openings and closings of the building.

dialeg building construction

There are two possible options:


This is the ideal situation. Here we should not incorporate any value in dialogue “building construction” and should be:

build constr. sense override


In this situation use dialogue to incorporate thermal properties we want to have each of the different closures and openings. In this way, each and every component of the building will inherit the properties we have chosen.

We can find the ability to have certain areas of the building that their closing properties differ from those specified generically to the entire building in the dialogue “building construction”, in this case, and without leaving the dialog “heating and cooling loads “We must use the tab” details “, here you can edit the characteristics of each individual space.


If we open the dialogue “construction type” of a specific space, we see the dialog that opens is almost identical to what we used to edit the properties of the whole building enclosures, here we can create templates that we want (I have created with the name “prueba”) and use it to the spaces we want.

construction type

Default is loaded a template with the name “building”, the properties of enclosures that template can not be edited, as are the values ​​we have awarded anteriomente in dialogue “building construction”.

In the two scenarios that have been raised above will always find a way to force the desired thermal properties by “clicking” on the override box column.


Checking the transmittance of the walls

Despite preconceived confidence when working with Autodesk software, is good from time to time make some little comparison exercise software to see if you have similar values. In this case, related to the calculation of thermal loads, I wanted to see if the transmittance of the walls which facilitates the Autodesk wiki with documents, is the same with Design Builder.

The Wall is the chosen “standard wall construction B”


I created the same wall with Design Builder:


The comparative results are almost identical, as is obtained with Revit 0.2993 W (m² x º K) and 0.300 W Design one (m² x K).

Also commented A3D forum.