Before we create constructions, it is important to note that there are two types of constructions in eQUEST, quick constructions and delayed constructions.
Side note: In reality, all constructions are delayed since they have thermal mass and therefore a time-delay on temperature changes. The math required to solve for heat transfer through delayed constructions is much more complicated than a UA∆T calculation. Instead, it uses transfer functions. Althought, eQUEST still uses transfer functions in quick constructions, these generic lightweight materialss are more similar to the U value approximation!
Before we get to the creating of either one of these material types, it is important to note the circumstances that indicate when to model a quick construction. We already mentioned the first circumstance (when modeling very low mass constructions, ie, lightweight wood). However, another common circumstance is when a construction represents a barrier between two spaces with a constant (or near constant) ∆T. This particular scenario is okay because we can assume a steady state heat transfer. At steady state, the transfer functions simplify to UA∆T and therefore can be represented by a quick construction. There are other possible scenarios, but they are left at the user’s discretion.
Under almost all other circumstances, a user should model a delayed construction, especially in cases of “heavy” construction materials. If the exact material mass is not obtainable, it will suffice to use similar mass materials and use the known u-factor.
Having discussed the issues, let’s take a look at how to model each type:
To make a quick construction:
1) Right click on the project name, in the “building shell” screen 2) Give the construction a name and select “create from scratch” and “U-value input” 3) Click “done” and you will be taken to the Construction Properties 4) Adjust the default values (optional) and click done
Please note: The resulting wall consists of several “lightweight” layers and thus a quick wall
To make a delayed construction:
Before making a delayed construction, a user must think “backwards”, Constructions consist of layers, which consist of materials, so it follows that the order of creation should be:
Materials-->Layers-->Constructions
Assuming we are already in detailed edit mode:
Create Materials: Create at least one material using the following: 1) Right click any material and select “create material” 2) Name the material, select “create from scratch” and select “Properties” for the material type 3) Press “ok” and you will be prompted to enter the known properties, please note the units
Create other lightweight materials: 1) Right click any material and select “create material” 2) Name the material, select “create from scratch” and select “Resistance” for the material type 3) Press “ok” and you will be prompted to enter the known resistance, please note the units
Once all materials are created:
Create a custom Layers: 1) Right click the layers folder, when in the building shell module 2) Give the Layers a name and select “create from scratch” 3) Press ok, and fill in the prompt with the material of the outermost layer 4) complete the prompts by selecting the proper Category and entry. 5) Press ok, and you will be taken to a Layers tab. 6) Complete the remaining layers from outside to inside, with the innermost layer being at the bottom.
Once layers are complete: Create a delayed construction:
1) Right click on the project name, in the “building shell” screen and select create construction 2) Give the construction a name and select “create from scratch” and “Layers Input” 3) Click ok, and select the layers previously determined 4) Adjust the remaining properties as necessary (Surface Roughness, Ext. Color, etc) 5) Please note that the U-value excludes the surface resistance which is determined hour by hour.
Once completed the new construction may be assigned to any surface by editing that surface and selecting the construction type under the field “construction”. The spreadsheet view works best to assign the construction to multiple rooms.