What is Thermal Isolation?
As any builder or developer knows, constructing commercial buildings is expensive. However, while there is often little room to maneuver in terms of reducing material and land costs, reducing the price of long term ownership by lowering utility bills via energy efficient building practices is much more feasible and has recently become a focus of the construction and facilities management industry. Having more efficient, sustainable structures not only defrays the costs of building components like lighting and controls, but power companies often provide rebates too, further justifying the expenses. Energy efficiency is particularly important when it comes to heating, ventilation, and air conditioning (HVAC), which composes 40 percent of the total utility costs and up to 10 percent of the average total cost of ownership of a commercial building of any kind.
Unsurprisingly, geographic location and climate also have a major impact on the amount of heating or cooling a building requires, and in turn the costs associated with maintaining the building. Trying to reduce the effect of the climate on HVAC costs has been studied for decades and a number of solutions have been found, one of the most popular being thermal isolation. Thermal isolation essentially refers to a structural component that provides a barrier from outside temperature. In commercial applications, there are two well-known options that produce thermal isolation, double facades and rainscreens. Both of which operate by creating an air gap between the outer skin of the building and the internal structure.
In this article we explore thermal isolation, its benefits, how it is best achieved, and how it is used to construct sustainable, energy efficient buildings.
Thermal Isolation vs. Insulation
To be clear, the term thermal isolation is a separate concept from the idea of insulating a building using fiberglass and related polymers. The goal of insulation is to simply help retain energy expended into the building (in the form of either heating or cooling) and prevent it from escaping. Rather with thermal isolation, the goal is to create a structure that allows occupants to control and set the temperature to their desired levels without excess influence from the elements outside. In other words, insulation is all about making the most of energy put into a building, while thermal isolation is concerned with reducing the amount of energy required to achieve the desired interior climate in the first place. The difference is critical because in many thermally isolated energy-efficient residential designs, as well as most common commercial real estate, a dual-layer approach to exterior cladding is common, where as insulation simply reinforces or thickens a single layer.
Rainscreens and Double-Skin Facades
A wall is intended to provide a variety of protections to the occupants and internal systems of the structure it encloses: resistance to temperature, protection from wind and water, reduction of noise, and visual and sonic privacy. It is nearly impossible to achieve all these benefits with a single layer of homogenous material; in nature, it is easy to see why dogs and other animals often have dual coats with a wiry, harsh outer layer and a downy inner coat. Thermally isolated commercial buildings also often operate under a similar principle, using two separate layers made of different materials to protect the structure from the elements. As mentioned before, this is often achieved via one of two structural techniques: rainscreens and double-skin facades.
A rainscreen system is more or less what it sounds like, an outer layer that provides waterproofing is installed set-off from the building to create an air gap. The creation of a drainage channel, as well as the air gap, prevents moisture from getting trapped and causing mold or mildew related structural damage. That air gap also serves as an insulating layer, decreasing the transfer of heat between building and outside elements, providing thermal isolation.
A building with a double-skin facade takes the double-layer-with-air-cavity concept posited by the rainscreen to the extreme: it is literally a building with two outer facades, usually with a relatively large (when compared to a rainscreen) air cavity in between. In the most advanced examples, this cavity is ventilated with fans or climate controlled with independent HVAC systems. For example, The Gherkin in London takes advantage of specialized windows that are mounted in two layers to help thermally isolate the building. A double-skin facade offers robust thermal isolation and is very efficient in the long term. However, the initial cost makes it less viable in the majority of commercial real estate projects, except where there are already high fixed costs, such as in land in London, San Francisco, New York City, and other major metropolitan areas.
Benefits of Thermal Isolation: Commercial Real Estate and HVAC Costs
If walls could magically float, rainscreens would not be necessary and most of the fundamental laws of physics would be lost. Unfortunately, thermal bridging is a real issue in commercial building and rainscreens are often used as one way to remediate that. While their primary benefit is to reduce moisture build-up, the fact that light, rain and wind first impact the outer shell aids significantly in the need for thermal isolation.
The primary issue here is the bridging, or heat transfer among the different layers of materials. In residential construction, the efficacy of insulation can be reduced by up to one-third, according to some estimates, because of the fact that the insulation is layered in between the wooden studs. Since the outer siding is directly connected via these studs to the interior walls, the interior envelope has small breaks every 18 to 24 inches that are more affected by changes in outside ambient temperatures.
Rainscreens avoid this by using systems of rails that create an additional two layers of protection, one via the gap and the second by allowing a different material to be used as the sheathing component underneath the outside cladding. However, as might be obvious, the mounting system itself must also be considered.
For example, aluminum is a very inexpensive metal that is commonly used in mounting systems, although other materials may be used. Unfortunately, its coefficient of thermal expansion is extremely low in common formulations. Without accounting for this in designs, many architects may be throwing away the benefits of thermal isolation by considering rainscreens. Many manufacturers of rail mounting systems for rainscreens that focus on thermal isolation now use polymer buffers. The material helps to maintain the cost-effectiveness of aluminum as a material without increasing the likelihood of bridging.
Benefits of Thermal Isolation Through Rainscreens: Maintenance, Mold Remediation, and Aesthetics
The dominant benefit of a rainscreen system remains the most valuable one: using two different types of materials with an air gap of some kind reduces the likelihood of adverse weather from damaging materials like wall-cladding that would otherwise be at risk for water damage.
The sheathing on the outside can be made from a variety of materials, from concrete to slate to a variety of polymer materials. In all cases, they are designed to provide excellent protection from both driving rain and condensation buildup that would otherwise accumulate on the interior
wall itself. However, the design itself also helps to limit the buildup of water through two other features: the drainage plane and the moisture-air barrier.
Rainscreens and their anchors are designed to allow for an air gap between the outside facade and the exterior wall. This air gap creates the opportunity for evaporation and drainage without the existing moisture ever reaching the other wall of the cavity. Further, through proper design, the drainage planes between the panels allows for excess water to move away from the veneer itself.
These require temperature differentials in order to work the best. For example, if the interior of a structure remained colder than the outside, such as in temperate climates during the summer, condensation would naturally build up on the insulated interior wall, rendering much of the rainscreen useless. Instead, the design limits the buildup of fluid and resulting mold because of the ability for moisture to evaporate.
Rainscreens can also add aesthetic value to a building. Clever and creative architects and designers are often able to devise unique, modern panel configurations and facade designs that add to the curb appeal of commercial properties. Additionally, by shuttling water away from the outermost visible layer of the building, exterior stains, corrosion, and run off trails are less likely to develop.
Other Options with Thermal Isolation: Vacuum-Insulated Panels
Many retrofit and refurbishment projects rely on the benefit of the air gap in double-facade construction in order to limit vapor damage, and now the most common designs focus on increasing the value of vacuum-insulated panels. Rather than deal with the dirty and hazardous fiberglass insulation, these panels can provide significant thermal isolation benefits without the hassle of working within existing structural envelopes.
Moreover, they do not have issues regarding thermal spillover into studs or related materials that decrease the efficacy of standard batt insulation. While they are not ideal for specialized designs, due to manufacturing design requirements, they can provide even more thermal resistance and limit water and vapor entrance in a double-facade system.
As a result, along with mounting double-facade panels, they are often used by architects to apply for rebates from local and state agencies for LEED and Green Building Assistance compliance.
Installing Rainscreen Systems
One primary issue in any exterior renovation or construction project is scope. Some projects have hundreds of thousands, if not millions of square feet of surface area to be covered by sheeting systems. Many companies make the sheeting out of various polymer materials, however, perhaps even more are engaged in creating the systems to hang these panels.
Many rely on a rail system that allows these sheets to be rested and attached to either vertical or horizontal brackets. However, this can lead to installation issues when it comes to assessing manpower needs. For many systems, it requires more than one person, where one is fixing the rainsheet wall to the brackets while the other is helping to align it properly during installation.
Just as certain advancements have helped reduce the human cost of commercial real estate by lowering utility bills, so too can construction project managers do so by opting for certain types of wall brackets. In this case, offerings from Monarch Metal enable installers to temporarily hold a panel in place with a secondary “leg” or “helping hand” for ease of mounting, and then continue installation. This significantly reduces the number of laborers involved in the installation of any one panel.
In addition, using systems that do not rely on direct connections to the interior wall also improve thermal efficiency. The break noted above reduces the likelihood of heat transfer towards the interior wall and reduces HVAC costs as a result.
Sourcing is also important when it comes to streamlining the inclusion of rainscreen systems. Specifiers and other stakeholders prefer to work with the smallest number of suppliers to reduce paperwork and hopefully find cost savings. Finding manufacturers whose panel mounts are compatible with a variety of panels and have working relationships with them can make project managers lives much easier.
Learn More About Monarch Metal Panel Mounting Parts for Thermal Isolation
There are a number of different providers for rainscreen mounts that will help you design the right system of cladding materials and rails for your specific application. Choose one that combines experience, quality materials and skill in working with a variety of construction project managers and architects.
Monarch Metal has been a premier supplier of vertical and horizontal rails for rain screen applications. Find more information about our offering here or contact us to talk about your next project today.