Thermal Comfort

GeoConcept Geothermal, HVAC and plumbing Consulatnts

Experts Conseil en Mécanique du Bâtiment

What is Thermal Comfort?

According to the ANSI/ASHRAE Standard 55-2010, thermal comfort is defined as “that condition of mind which expresses satisfaction with the thermal environment and is assessed by subjective evaluation. ”Also known as human comfort, thermal comfort is the occupants’ satisfaction with the surrounding thermal conditions and is essential to consider when designing a structure that will be occupied by people.

 

Thermal comfort is difficult to measure because it is highly subjective. It depends on the air temperature, humidity, radiant temperature, air velocity, metabolic rates, and clothing levels and each individual experiences these sensations a bit differently based on his or her physiology and state.

 

A cold sensation will be pleasing when the body is overheated, but unpleasant when the core is already cold. At the same time, the temperature of the skin is not uniform on all areas of the body. There are variations in different parts of the body which reflect the variations in blood flow and subcutaneous fat. The insulative quality of clothing also has a marked effect on the level and distribution of skin temperature. Thus, sensation from any particular part of the skin will depend on time, location and clothing, as well as the temperature of the surroundings.

 

Factors in Human Comfort

 

Here are six factors to take into consideration when designing for thermal comfort. Its determining factors include the following:

 

Metabolic rate (met): The energy generated from the human body.

Clothing insulation (clo): The amount of thermal insulation the person is wearing.

Air temperature: Temperature of the air surrounding the occupant.

Radiant temperature: The weighted average of all the temperatures from surfaces surrounding an occupant.

Air velocity: Rate of air movement given distance over time.

Relative humidity: Percentage of water vapor in the air.

The environmental factors include temperature, radiant temperature, relative humidity, and air velocity. The personal factors are activity level (metabolic rate) and clothing.

 

Variable Air Volume System:

Variable Air Volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system. Unlike constant air volume (CAV) systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant temperature. The advantages of VAV systems over constant-volume systems include more precise temperature control, reduced compressor wear, lower energy consumption by system fans, less fan noise, and additional passive dehumidification.

Design Considerations for thermal comfort optimization

Multi-Split System and Variable Refrigerant Volume (VRV) or Variable Refrigerant Flow (VRF)

A multisplit Air conditioning and Heat pump system consist of one Outdoor Unit (condensing unit) and multiple indoor units (evaporators).

 

Variable refrigerant flow (VRF) or variable refrigerant volume (VRV) is an HVAC technology invented in Japan by Daikin company in 1982. Indoor Units (or Evaporators or Fan-Coil-Units) use refrigerant as the cooling and heating medium. This refrigerant is conditioned by a single outdoor condensing unit, and is circulated within the building to multiple fan-coil units (FCUs).

 

Advantages of VRV multi-split system is higher energy efficiency and a better customized temperarture control. Energy efficiency is at its peak for models with simoultaneous heating and cooling, where heat is extracted from places with cooling demand and diverted to places with heating demand.

Indoor Floor Heating System

Radiant Underfloor heating (RUFH) has become a viable method of space heating due to significant advances in heating technology and the increase in raw material costs of copper and steel used in radiator heating systems. When considering your underfloor heating options, it is important to bear in mind the advantages and disadvantages of the various options available.

 

The Advantages of Underfloor Heating:

  • Clears rooms of ineffective, impractical, unsightly wall-hung radiators
  • Saves from 15% to 50% on heating bills
  • Carries virtually no maintenance costs
  • Prevents dust gathering behind radiators and circulating around the room – ideal for sufferers of asthma or other respiratory issues
  • Eliminates dust mites from carpets
  • Underfloor heating provides 70% radiating heat, offering a more comfortable climate than radiators
  • The thermal mass of an underfloor heating systems provides warmth for longer after switching off than would traditional radiators
  • Evaporates dangerous water spillages quickly from bathroom and kitchen tiles
  • Underfloor heating runs quietly, with none of the creaks and groans of old copper pipes
  • Can be used with almost any flooring type including stone, laminate, hardwood, lino, and carpet (below 1.5 Tog)

 

The disadvantages of underfloor heating

  • Underfloor heating can take longer to heat up than traditional radiators
  • Care must be taken with certain furniture with underfloor heating, it is recommended to place pianos on insulation
  • Retro-fitting underfloor heating can be expensive and impractical
  • Underfloor heating must be well designed, it is difficult to change or adapt the system once installed.

Direct Digital Control (DDC)

The heating, ventilation, and air conditioning system (HVAC) is the heart of many of the systems in the structure. The HVAC system often determines the happiness of the people who live in your building.

 

It helps keep people cool in the summer. It provides a barrier against extreme weather conditions in the winter months. And it keeps people healthy and safe by monitoring and handling levels of naturally occurring pollutants throughout the building.

But with the complicated systems of today, it can be difficult to maintain control of hundreds of interrelated systems without computer assistance. That’s where Direct Digital Control (DDC) systems come in.

Today’s standard for monitoring indoor environmental conditions, DDC systems evaluate inputs like temperature and humidity levels, and send outputs that control heating valves and regulate outside air. And with the proper design parameters in your structure, DDC systems will save you money via reduced energy costs. Here are three benefits of using DDC for your HVAC system.

 

  • Central monitoring and control. With DDC systems, your operators can monitor and change system operations instantly, from one central location.
  • More accurate energy management. DDC systems use electronic rather than pneumatic sensors, enabling higher degrees of accuracy with temperature control, leading to significant energy savings.
  • Improved data analytics. As a building operator, you’re always looking for data that can help you streamline building systems for optimal performance and efficiency. DDC systems include data management and analysis tools that show you trends for critical or problem areas and help you make future improvements.
  • DDC gives the ability to customize your equipment's control sequences that conventional control don't. the result is higher thermal comfort and better occupant satisfaction.

Outdoor Snow & Ice Melting

Winter can be an exciting time of year, especially for sport enthusiasts — snowmobiling, sledding, skiing, hockey. But along with the fun comes shoveling, plowing, sanding and salting — as well as the danger of slipping and sliding and the injuries that can result.

 

Whether for residential, commercial or industrial applications, Snow & Ice Melting systems provide a safe, reliable and economical alternative to snow removal. Snow & Ice Melting systems circulate warm fluid through PEX tubing buried in concrete, asphalt or a sand bed. The fluid heats the slab until it is warm enough to melt the snow and ice. The system can be controlled simply with an on/off manual switch or be programmed to function automatically. Snow & Ice Melting systems can be used in a variety of applications. These systems are often used in areas where safe, clean and easy access is critical, including: Driveways, Sidewalks, Stairs, Building entrances, Loading docks, Hospital emergency entrances, Wheelchair access ramps, Parking ramps, Parking lots, Helipads.

Snow and ice melting systems can also help

 

comply with Americans with local Disabilities regulations for safe and easy access. Convenience is another major factor when considering a snow and ice melting system. Snow & Ice Melting systems provide:

Safety — Ramps, sidewalks, driveways and steps are free of snow and ice all year long. Accidents are less likely to occur on pavement where snow and ice has not accumulated. Surfaces dry faster and are safer when a Snow & Ice Melting system is operating underfoot.

Reduced Maintenance — No more shoveling, plowing, sanding or salting. No more replacing sod and landscaping damaged by expensive snowremoval equipment. Additionally, carpets are cleaner and last longer because snow and salt are not tracked over them.

Increased Pavement Life — Freeze and thaw cycles can be eliminated, extending the life of concrete, asphalt and especially those hard to shovel or plow brick pavers. Additionally, the infrastructure of parking ramps is not damaged by corrosive chemicals used to melt snow and ice.

Energy Savings — Snow & Ice Melting systems can be designed to take advantage of existing energy sources. For example, facilities using geothermal energy as a primary heat source, which excess heat at moderate winter termperatures. the excess energy can be transfered to hot fluid and used for Snow and Ice melting. The use of waste energy provides a virtually cost-free system operation.