utsa-design strategies for comfort

Quality Passion Knowledge

Design Strategies for Comfort

Building Technology IV University of Texas, San Antonio

IBS Advisors

Consulting Education MediaProvider

Brett Dillon• Managing Director, IBS

Advisors, LLC

• Member, RESNET Board of Directors

• Chair, RESNET Technical Committee

• Member, RESNET Training & Education Committee

• USGBC LEED for Homes Green Rater Faculty™

• RESNET-accredited Trainer

• RESNET-accredited Quality Assurance Designee

• 4th Generation Builder

• Author of books on:

• HVAC

• Weatherization

• Advanced building techniques

• HERS Ratings

5 Comfort Factors

Structure

Systems

Commissioning

Surrounding Air

Temperature68º F, heating 78º F, cooling

Moisture Levels in Air

30%-50% RH < 80º F Dewpoint

Velocity of Airflow

> 25 fpm < 50 fpm

Evaporative Rate

Related to Moisture Related to Air Velocity

Clothing Levels

Related to Culture & Lifestyle

Temperature Control

Shelter from sun Maintain warmth

Garage Living

Space

Living Space

Living Space

Temperature Controls

Shade

Temperature ControlsSolar

RadiationAbsorptance

Transmittance

Albedo

Temperature Controls

Uave = (U1 x A1) + (U2 x A2) / Atot Q = U x A x ΔT

Temperature Controls

Siding, 1.5

WRB, 58

OSB,

Insulation, varies

Primed & Painted Drywall,

2

Building Material ~ Perm RatingFiber cement siding 1.5

OSB 0.75Primed & Painted Gypsum Board 2

Tyvek® Housewrap 58Cellulose 75Fiberglass 120

Open cell spray foam 10Closed cell spray foam 0.86

Airflow Velocity

Hole Pressure Difference

Stack Effect

Mechanical Systems

• Kitchen Range Hood

• Bath Exhaust

• Clothes Dryer

• Ducted HVAC

Evaporative Rate

Clothing Levels

SystemsSystem Concept

Load Calculation

Equipment Selection

Air Distribution

Duct Size Calculation

Adjust, Test & Balance

Manual RS

Manual J

Manual T

Manual S

Manual D

Heating CoolingT-stat setpoint 70°F 75°F

RH 25% 40%Temp @ T-stat 68°F - 72°F 72°F - 78°F

Room-Room or Level-Level ∆ T + 4°F + 6°F

Temp in any room + 2°F of set point + 3°F of set point

Floor temp over slab or unconditioned space > 65°F, 4” above floor

Filtration > MERV 8 > MERV 8

Ventilation 7.5 cfm/person + 1 cfm/100 ft2

7.5 cfm/person + 1 cfm/100 ft2

Duct Leakage < 6% < 6%

Spread

Manual T

Sensible Heat Ratio

Supply Air Room Air Temperature

Difference

< 80% 54 75 2180% to 85% 56 75 19

> 85% 58 75 17

Manual S

Manual D• Required under IRC M1601.1

• Implies room-by-room load calculation must be performed

• CFM

• SHR

• ΔT supply-return

• Sensible load

• Friction rate

• Pressure drop x 100 / total effective length

Supply Duct Sizing

• What temperature does the air need to be to meet the load?

• How many CFM of air must be delivered to meet the load?

• Sensible Load / (1.1 x ΔT)

Duct Layout

Trunk and Branch SpiderRadial

Courtesy of Building America Industrialized Housing Partnership, FSEC & Dennis Stroer

Commissioning

AAAS.org