NREL Provides Guidance to Improve Thermal Comfort in High-Performance Homes (Fact Sheet)

PDF Version Also Available for Download.

Description

This technical highlight describes NREL research to develop recommendations on HVAC system design and operating conditions to achieve optimal thermal comfort in high-performance homes. Researchers at the National Renewable Energy Laboratory (NREL) have developed recommendations to help residential heating, cooling, and ventilation (HVAC) designers select optimal supply inlet size and system operating conditions to maintain good thermal comfort in low heating and cooling load homes. This can be achieved by using high sidewall supply air jets to create proper combinations of air temperature and air motion in the occupied zone of the conditioned space. The design of air distribution systems ... continued below

Physical Description

2 p.

Creation Information

Creator: Unknown. January 1, 2012.

Context

This report is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided by UNT Libraries Government Documents Department to Digital Library, a digital repository hosted by the UNT Libraries. More information about this report can be viewed below.

Who

People and organizations associated with either the creation of this report or its content.

Creator

  • We've been unable to identify the creator(s) of this report.

Sponsor

Publisher

Provided By

UNT Libraries Government Documents Department

Serving as both a federal and a state depository library, the UNT Libraries Government Documents Department maintains millions of items in a variety of formats. The department is a member of the FDLP Content Partnerships Program and an Affiliated Archive of the National Archives.

Contact Us

What

Descriptive information to help identify this report. Follow the links below to find similar items on the Digital Library.

Description

This technical highlight describes NREL research to develop recommendations on HVAC system design and operating conditions to achieve optimal thermal comfort in high-performance homes. Researchers at the National Renewable Energy Laboratory (NREL) have developed recommendations to help residential heating, cooling, and ventilation (HVAC) designers select optimal supply inlet size and system operating conditions to maintain good thermal comfort in low heating and cooling load homes. This can be achieved by using high sidewall supply air jets to create proper combinations of air temperature and air motion in the occupied zone of the conditioned space. The design of air distribution systems for low-load homes is an integral part of residential system research and development in systems integration. As American homes become more energy efficient, space conditioning systems will be downsized. The downsizing will reach the point where the air flow volumes required to meet the remaining heating and cooling loads may be too small to maintain uniform room air mixing, which can affect thermal comfort. NREL researchers performed a detailed study evaluating the performance of high sidewall supply air jets over a wide range of parameters including supply air temperature, supply air velocity, and supply inlet size. They found that in heating mode, low and intermediate supply temperatures of 95 F (308 K) and 105 F (314 K) maintained acceptable comfort levels at lower fan powers than can be achieved at 120 F (322 K) supply temperatures. For the high supply temperature of 120 F (322 K), higher fan powers (supply velocities) were required to overcome buoyancy effects and reach a good mixing in the room. In cooling mode, a supply temperature of 55 F (286 K) provided acceptable comfort levels. A small supply inlet of 8-in. (0.2 m) x 1-in. (0.025 m) is recommended in both heating and cooling modes. Computational fluid dynamics was used to model heat transfer and airflow in the room. The technique consists of using the model output to determine how well the supply air mixes with the room air. Thermal comfort is evaluated by determining the Air Diffusion Performance Index (ADPI). The level of comfort is evaluated by monitoring air temperature and air velocity in more than 600,000 control volumes that make up the occupied zone of a single room. The room has an acceptable comfort level when more than 70% of the control volumes meet the comfort criteria on both air temperature and air velocity. Figure 1 illustrates the plots of acceptable draft temperature, which is between -3 (-1.7) and 2 F (1.1 K) for two supply velocities of 394 fpm (2 m/s) (a) and 788 fpm (4 m/s) (b) when the room was supplied by 55 F (286 K) air. The plots show the distribution at selected cross-sections along the room. Colored regions on each cross-section are considered comfortable (blue regions are on the cold side and red regions are on the warm side). Regions of acceptable draft temperature are larger at low velocity and decrease as the velocity increases. As a result, the supply velocity of 394 fpm (2 m/s) provided higher comfort level than the supply velocity of 788 fpm (4 m/s). Work is in progress at NREL to extend this research to evaluate additional configurations and to integrate this system into a whole-house context.

Physical Description

2 p.

Source

  • Related Information: Building America: Technical Highlight, Building Technologies Program (BTP)

Language

Item Type

Identifier

Unique identifying numbers for this report in the Digital Library or other systems.

  • Report No.: DOE/GO-102012-3492
  • Grant Number: AC36-08GO28308
  • DOI: 10.2172/1033447 | External Link
  • Office of Scientific & Technical Information Report Number: 1033447
  • Archival Resource Key: ark:/67531/metadc833282

Collections

This report is part of the following collection of related materials.

Office of Scientific & Technical Information Technical Reports

What responsibilities do I have when using this report?

When

Dates and time periods associated with this report.

Creation Date

  • January 1, 2012

Added to The UNT Digital Library

  • May 19, 2016, 3:16 p.m.

Description Last Updated

  • April 4, 2017, 6:23 p.m.

Usage Statistics

When was this report last used?

Yesterday: 0
Past 30 days: 0
Total Uses: 2

Interact With This Report

Here are some suggestions for what to do next.

Start Reading

PDF Version Also Available for Download.

Citations, Rights, Re-Use

NREL Provides Guidance to Improve Thermal Comfort in High-Performance Homes (Fact Sheet), report, January 1, 2012; Golden, Colorado. (digital.library.unt.edu/ark:/67531/metadc833282/: accessed August 17, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.