Introduction To HVAC Design Concepts
All customized HVAC analysis and design services will adhere to the installation and operating objective of SIMPLE SYSTEMS PERFORM RELIABLY and are ECONOMICAL.
HVAC BASICS
OVER-Sizing an HVAC system is detrimental to energy use, comfort, Indoor Air Quality, building sustainability and equipment durability. These associated characteristics are generated by systems that “short cycle” in the heating and/or cooling modes. Best operational efficiency and effectiveness is maintained by a heating and cooling system OPERATING FOR LENGTHY PERIODS to address the constantly varying loads. ANALOGY : An automobile driving at a steady speed on the highway achieves best fuel economy, while speeding up and slowing down creates undue wear and tear on the engine and braking systems, and reduces fuel efficiency.
RIGHT SIZING of the HVAC system begins with an accurate assessment of the heating and cooling loads within a space. The values determined by the heating and cooling load calculation process provides requirements for the equipment selection and the duct design needed to deliver conditioned air to the rooms of the building to meet the occupant’s comfort expectations.
The best practices for ventilation and Indoor Air Quality (IAQ) will adhere to the ASHRAE 62.2 -2013 residential criteria and the ASHRAE 62.1 commercial criteria. Infiltration will initially be presumed for New Construction ( post-2020) residential projects as 0.24 Air Change per Hour (A.C.H.) Natural
Genral local and state
Energy Conservation (EC) Requirements
The International Building Code (IBC) and Florida Building Code (FBC) require that all new construction be analyzed per either ACCA Manual J or N to determine the HVAC requirements as provided in a set of architectural plans and the material specifications. Specifically, FBC Residential Section, Chapter 11 Energy Efficiency states FBC section Energy Conservation (EC) shall be applied to all new buildings
Heating and cooling equipment shall be sized in accordance with ACCA Manual S based on the equipment loads calculated in accordance with ACCA Manual J or other approved heating and cooling calculation methodologies, based on building loads for the directional orientation of the building. The manufacturer and model number of the outdoor and indoor units (if split system) shall be submitted along with the sensible and total cooling capacities at the design conditions described in Section R302.1. This Code does not allow designer safety factors, provisions for future expansion or other factors that affect equipment sizing. System sizing calculations shall not include loads created by local intermittent mechanical ventilation such as standard kitchen and bathroom exhaust systems. New or replacement heating and cooling equipment shall have an efficiency rating equal to or greater than the minimum required by federal law for the geographic location where the equipment is installed.
The mechanical requirements for each state are generally quite similar because they are based on the International Mechanical Code ( IMC). The International Residential Code (IRC) is available for review using the following link.
SECTION EC, R 403.7 Heating and cooling equipment (Mandatory).
R 403.7.1 Equipment Sizing
CHAPTER 14 HEATING AND COOLING EQUIPMENT APPLIANCES
Heating and cooling equipment and appliances shall be sized in accordance with ACCA Manual S or other approved sizing methodologies based on building loads calculated in accordance with ACCA Manual J or other approved heating and cooling calculation methodologies.
FSEC – Florida Solar Energy Center / Energy Gauge . Form R405 -2017 ENERGY EFFICIENCY CALCULATIONS Also, Res Check software is a general calculation procedure used in many States.
The efficiency measure used in making any enhanced performance equipment selection will be the most beneficial for comfort and IAQ, as well as reasonable HVAC System operating costs in your locale.
General design and engineering service fees along with schedule commitment are provided on the following page.
SIMPLIFIED HVAC and MECHANICAL SYSTEMS DESIGN, LLC
DUCT DESIGN CONSIDERATIONS by RSES
References, Information and Links
DUCT DESIGN CONSIDERATION
Figure 3 provides an effective layout for minimizing the External Static Pressure.
Professional Resources & Standards
1
RSES
Refrigeration Service Engineers Society
Professional organization providing technical education and certification for HVAC/R technicians and engineers.
2
HVAC Systems Design
HVAC Systems Design Handbook by Robert W. Haines
Comprehensive guide covering system design principles, load calculations, and equipment selection.
3
IRC & ICC
International Residential Code & International Code Council
Building codes and standards for residential construction including HVAC installation requirements.
4
EERE
Office of Energy Efficiency and Renewable Energy
U.S. Department of Energy office focused on energy efficiency technologies and renewable energy solutions.
5
Building Science Corp
Building Science Consulting & Architecture
Full service architecture firm specializing in building science consulting and high-performance building design.
6
ASHRAE
ASHRAE Fundamentals, Chapter 14 - Climatic Conditions
American Society of Heating, Refrigerating and Air Conditioning Engineers - fundamental principles and climate data for HVAC design.
7
ACCA
ACCA Standard 5 - HVAC Quality Installation Specification
Air Conditioning Contractors of America - Quality installation standards for HVAC systems.
8
ASHRAE 62.1
Ventilation for Acceptable Indoor Air Quality
Standard covering ventilation requirements for commercial and institutional buildings to ensure acceptable indoor air quality.
9
ASHRAE 62.2
Ventilation and Acceptable Indoor Air Quality in Low-Rise Residential Buildings
Residential ventilation standard for single-family homes, townhouses, and low-rise multifamily buildings.
10
Design Issues
HVAC System Design Issues
Comprehensive guide addressing common HVAC system design challenges and solutions.
11
NREL
Advanced Strategy Guidelines: Air Distribution Basics and Duct Design
Figure 1, HVAC Design Process - Advanced guidelines for efficient air distribution system design.
12
RESNET
Implementation Guidelines for the ERI Performance Path
Residential Energy Services Network implementation guidelines for Energy Rating Index performance path compliance.
Definitions
A.H.U.: Air Handling Unit _ A.S.H.R.A.E. : American Society of Heating, Refrigerating __ ________________________ _ and Air Conditioning Engineers __________________________________________________ _ EC: Energy Conservation __ ___ _ H.S.P.F.: Heating Season Performance Factor _ I B C: International Building Code _ S.E.E.R.: Seasonal Energy Efficiency Ratio _ S.H.G.C.: Solar Heat Gain Coefficient ( Window property) _ U-Factor: Transmissibility (1 / Resistance) of glass assembly or other materials
Building Thermal Envelope
The ‘thermal envelope’ of a building is the union of those structures that SEPARATE the CONDITIONED PART (subject to being heated and/or cooled) of the building from the OUTSIDE (including neighboring buildings). The pictorial indicates the roof, walls, windows, doors, ceiling, basement, infiltration {blue arrows} envelope as shown by the GREEN line at the building exterior.__________________________________________________
Equipment and duct schematic
Bedroom
Common Areas
Master Suite
Project Location
See U.S. IECC Climate Zone Map Regions 1 through 7
