- Overall HVAC design strategy
Based on the Insights analysis I had from the building envelope module, I picked what seemed to be the best alternative (low U-value, without being too extravagant and costly) for roof, exterior walls, and windows: R-38 walls, R-15 roof, double-glazing low-emissivity windows. I also decided to override the slab with a slab edge R-5 insulation. I calculated my heating & cooling loads based on these assumptions:
I ended with the following calculated heating/cooling loads and supply airflow:
Using Climate Consultant with Climate Zone 3 in California (Jasper Ridge Biological Preserve) and the California Energy Code Model, I got:
It seems like the best design strategies I should implement are: sun shading of windows, high thermal mass, natural ventilation cooling, internal heat gain (inherently part of the model), passive solar direct gain, wind protection of outdoor spaces, and heating (and cooling).
It's mostly what I have done with a lot of glazing on the South façade, with shading devices. My building as a whole will require mostly heating. However, the heating & cooling loads calculation show that rooms will require both heating and cooling, as well as natural ventilation.
I am going to implement an air transport HVAC system in order to provide fresh air at the same time as I am providing heating and cooling.
Heating strategy and implementation, cooling strategy and implementation, challenges:
I'm using a simple air-based HVAC system with an air handling unit on the rooftop, supply and return air ducts, supply and return air terminals, and VAV boxes per zone.
The layout for the 2nd floor looks like this: I am not sure if I should have branched it out to serve zones separately. I am struggling to add VAV boxes.
Also, running the system inspector, it looks like CFM values do not add up, which I am not sure why.
The return air ducts are above the supply air ducts to ensure that there won't be any problem.
In terms of supplied airflow, all rooms on the 2nd floor meet the requirements. Corridors do not but I think their location in the building (West facade) and the windows I strategically placed there will allow for a lot of natural ventilation.
An issue I ran in was that the air terminal units were on the rooftop and because of the green roof I added, the roof is thick. I had to modify the air terminal units so that they'd be connected to the room on level 2, by lowering the associated setpoint.