General HVAC Strategy:

My HVAC system is designed around the three main principles:

• Ventilation (as is a minimum building requirement)
• Heating loads (if you’re using an air-based heating system)
• Cooling loads (if you’re using an air-based cooling system)

My building located in Jasper Ridge Preserve, in California’s Climate 4 zone. As was outlined in the climate analysis in an earlier module (see psychometric chart below for a reference), heating and humididifaction is the primary component required to constitute a ‘comfortable environment’.

The first step was to identify all rooms and zones in the building. In order to best utilize Revits new HVAC analytical modelling, I assigned a unique HVAC zone for each room. This would give me a clearer breakdown of the individual peak heating and cooling loads. The graph below, shows the summary of the analytical spaces after running the model. The peak heating and cooling loads were used to calculate the heating and cooling CFM values, that would dictate the HVAC distribution across the building.

After the simulation was completed, and the data had been interpreted, I could go back and assign the different HVAC zones more logically. Overall I created 5 key zones, based around a variety of factors including temperature control requirements, proximitiy, and heating/cooling load sizes.

The table below, shows the final Space schedule, with the appropriate zones, specifiied supply and actual supply airflows. Two important things to note:

1) While I assigned an appropriate space type for each area, I decided to tweak the capacities, to better match my expected occupancy and thus airflow demand.

2) The entrance atrium and lobby have an actual supply airflow of 0, as they did not use the HVAC system, but were instead serviced by radiant floor cooling.

Overall, my HVAC system strategy is a fairly diversified one, as I am looking to capitalize on the benefits of individual systems. With sustainability in mind, I am attempting to design the most efficient system, in order to keep my building EUI at a low. Below, I have outlined and briefly introduced the concepts I will be applying:

Natural Ventilation & Cooling:

The mild climate and nearby lake make for a perfect environment in which to take advantage of passive cooling measures. Inspired by Y2E2s natural ventilated atrium, I have designed a similar concept in my building.

California has long summers with a significant amount of solar exposure. In combination with the large number of building occupants who radiate heat, natural cooling in the summer months is of paramount importance. I have designed a three story atrium with ventilated windows on the east and west sides, to allow for cross-ventilation, and cooling from the so-called ‘stack effect’. The stack effect is a natural process that relies on the difference in temperature and density between the indoor and outdoor air. As the warm air rises and escapes through the top windows, it creates a negative pressure inside the building that draws in cooler air from the outside through lower-level windows and doors, which creates a flow of fresh air throughout the space.

Radiant Floor Heating (Zone: Atrium):

Due to the large ceiling height of the main atrium and lobby, using air as a medium to hea the space in the cooler months would prove to be an inefficient system. Instead, a radiant floor heating system has been designed, and installed in the ground slab. As a result of this fluid-based system, heating could be evenly distributed in the space that the visitors occupy, rather than heating the large cavity of the second and third floor ceilings.

HVAC System:

My HVAC system can be split into two loops, with individual AHUs.

Loop 1 (Outdoor AHU, services zones: Exhibition Spaces & Office Spaces) :

The two wings of the building, constitute the three exhibition spaces and the office space. These spaces have a far larger occupancy than many of the other building areas, and would thus benefit from their own controllable temperature. For this purpose, I have split the exhibition spaces into one HVAC one, and the office space into another. Both are serviced by a main outdoor AHU, which lies in the cavity between the ceiling and solar roof, thus protecting it from the elements. According to the spaces schedule generated from the HVAC analysis, the AHU on roof would require 5160 cfm, and thus a 1.1 square meter of coil, horizontal Outdoor AHU with a max outlet capacity of 5999CFM was selected. This can be seen rendered in the screenshot below

As shown in the 3D model of the isolated loop, it spans across the two floors, and services every room with supply and return diffusers, set to the appropriate capacities to avoid overengineering and wasted energy. Similarly, the Revit duct sizing tool was utilized, to minimize material and energy wasted through inefficient design procedures.

A VAV box is conected to the main duct servicing the office space, to allow for personlized temperature controls in the office environemnt. Meanwhile, the main ‘trunk’ of the HVAC system runs through the mechanical room, along the stairs. On floor two, I will update the architectural model to enclose the ducts within gypsum walls to hide them from occupants views.

3D rendering of full Loop 1 HVAC System

Ground Floor Mechanical Plan View

First Floor Mechanical Plan View

Second Floor Mechanical Plan View

Loop 2 (Indoor AHU, services zones: Auditorium, Miscellanious Rooms & Lobby) :

The second loop, uses an indoor AHU in the ground floor mechanical room. It services mostly smaller rooms that together constitute their own HVAC zone (restrooms, cafe, workshop, etc.). Additionally, it services the main auditorium, which due to its large capacity, has its own VAV box so that its temperature can be regulated depending on capacity.

3D Rendering

Ground Floor Mechanical Layout

First Floor Mechanical Layout

Second Flor Mechanical Layout

Building & Challenges Overview:

The design provides heating, cooling and ventilation to all rooms in the building. The ducts are located at various heights, depending on whether its under a steel or column beam system. After careful advance planning, and flexible duct rearranging, I was ablte to produce a network of ducts that do not clash with any structural or architectural features. There is approximately 3m of headroom, which should be sufficient for a building of this type.

Additionally, the slanted roof of the audotrium provided some challenges, as you could not just set an appropriate distance from the roof for the HVAC system. This was particularly important since the elevated seating meant that the HVAC system needed to provide a max clearance at the back.

One of the biggest challenges I faced, was adjusting the duct elevations, and having them cross-over, while maximizing available head room. In the example below, I had to cross the ducts three times, in order to allow for the servicing of multiple floor levels. It took careful measuring and planning, and multiple attempts to succeed with this design choice.

While I like the look of the exposed columns, the ducts, VAV boxes and steel/concrete beams will be hidden from view with a suspended ceiling, like shown below. This allows for good ventilation through the ceiling, while looking natural and aesthetic