Q&A - Talbott Solar Radiant xLath™

You asked, we answered

With the help of our past clients, we have compiled a Q&A that answers almost all questions about radiant heating and cooling:

Why is a radiant heating and cooling system more efficient than a forced air system?

The mechanical equipment is similar, but operation cost is lower for pumps than for blower motors; both distribute the building's energy.

Back losses from the radiant panel are generally less than duct losses.
The mechanical equipment operates more efficiently and building envelope losses can be lower because:

a. Radiant heated rooms may be comfortable at a lower temperature.
b. Radiant cooled rooms may be comfortable at a higher temperature.

A well designed radiant panel system can use less energy than a forced air system for the same space.
Some people desire more drastic operation levels to create a custom temperature. This is not a problem because radiant will always create a more comfortable ambient temperature. If you choose to set your system to drastic temperatures, your compared operation costs may be similar to that of a forced air system.
A badly designed radiant system can use more energy than a well designed forced air system.

Are radiant ceiling panels only for new construction sites?

No. Radiant heating and cooling can be installed in new construction sites as well as retrofit into existing buildings.

I have only heard of radiant cooling tubing under flooring or in concrete. What are the advantages of an xLath ceiling installation?

The key advantage is easy access to tubing in the instance that it needs a repair. xLath repairs are uncommon, however, if there was a leak, it is much easier to detect and contain when compared to a leak under the floor. Furthermore, it is much more cost effective to replace drywall and paint rather than expensive flooring.

Do radiant ceiling panels need to be horizontal?

Radiant ceiling panels can follow any ceiling contour the building designer desires. Radiant heat (and cold) travels in straight lines at the speed of light. Keep in mind that an object which we cannot "see" , or is "shaded" from the radiant panel will be cooler in the heating season (and warmer in the cooling season) than objects in line of sight of the radiant panel. For instance a canopy on a four poster bed would be hotter or colder hold than the bed because it is shading the actual bed.

Is radiant conditioning more comfortable than a forced air system?

Most people are more comfortable in a radiant conditioned space. There are no drafts or no noise in a properly designed radiant system. Heating and cooling system design and individual preference can make a big difference in perceived comfort.

The Talbott crew working as a team to install xLath™

Is it harder to install radiant than conventional ducted forced air system?

In some cases it may easier to condition an existing building with a radiant heating and cooling system rather than a ducted forced air system. Why? The ceiling does not have to be lowered as much because radiant takes up less space, resulting in higher ceilings. As an example, for new construction the ceiling is lowered only 1 1/8", and an even smaller 5/8" is needed for a retrofit before being sheet rocked. The architectural impact on the building design is minimal in most cases.

Can I use a geothermal heat pump to heat and cool my radiant building?

Yes. Geothermal heat pump systems work very well with radiant panel heating and cooling systems. The low temperature heating and high temperature cooling design of the radiant panel system helps the geothermal heat pump to operate efficiently.

How will I know that my radiant heating and cooling system is working?

If you are comfortable, your system is working. Radiant heating and cooling systems are silent, and do not create drafts. You might be able to hear the boiler or chiller if you listen closely, but they not in the inhabited space and operate intermittently.

Does this system produce any noise?

We found that when using PEX with an EVOH coating, ticking occurred. Since this experiment, we have taken the proper measures to always use a Polyethelyene finish on tubing. This coating protects the tubing when the running water runs through the system, leaving no ticking sound.

Is a building with a radiant ceiling system responsive to thermastat changes?

A building with a radiant ceiling system responds very quickly to thermostat inputs and begins to achieve comfort in a few minutes. Therefore, there is no need to anticipate occupancy to pre-condition a building before it is to be used. If we compare this rapidly responsive system with a traditional forced air cooling/heating system that takes at least 30 minutes to reach a temperature goal, we can see quickly which option is best. However, if you have a building with radiant slab, it may take several hours to achieve comfort.

Is heating from the ceiling uncomfortable?

Heating from the ceiling resembles the way the sun heats the earth. However, this type of heating is not a noticable blast of heat. Rather, the ceiling directs its heat to surfaces and furniture around the house, only heating it to a comfortable temperature that you select. If you do notice that the ceiling is uncomfortably warm, this indicates that the supply water temperature is too high, and should be set a little lower. This lower temperature will result in a longer on cycle and fewer starts for the boiler, resulting in greater economy as well as greater comfort.

What about mold?

It is no secret that mold grows in damp locations. This dampness is created when water leaks or condenses on surfaces. We have avoided any problems with mold growth by specifying that the circulating hydronic water remain above the dew point within the conditioned space. Therefore, mold problems will be the same as or less than in traditional air conditioned buildings. A properly designed and operated radiant panel cooling system will not promote mold growth.

Yolo Habitat for Humanity's completed xLath™ affordable housing project

Will humidity be a problem?

It all depends on your location. Radiant panel systems shall never be operated to dehumidify the indoor air. In a hot humid climate, a forced air dehumidification system will be required. In a hot dry climate dehumidification will not be required. In moderate humidity climates, controlled ventilation, or mechanical dehumidification will be used.

My west-facing unshaded bedroom gets unbearably hot during the summer. Will xLath models be enough to keep it cool?

In one of our trial projects, we encountered problems estimating the room load of a west-facing, unshaded room with a large window. We solved this problem by adding supplemental xLath modules to this type of room to intercept the heat and remove it before it has the chance to warm the room.

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