“Layton Consulting Fenestration Nerds” By Anton Van Dyk: And the Survey Says… Project Specific Thermal of Fenestration is a Design Item.
Several weeks ago, I posted a survey on LinkedIn regarding the best time to perform a project-specific thermal evaluation of fenestration products for a building. 86% voted for the design stage as opposed to the shop drawing stage.
I raise this question as we are seeing a cultural shift in how we design buildings and apply codes and regulations. In particular, the biggest shift in how we apply energy codes as buildings become more and more energy efficient. This shift is happening faster than any shift in code history. Well, the addition of energy codes is not new, what is new is that the level of energy efficiency is moving at a pace many struggle to keep up with. Both, in product ability and in the process of how that product is applied.
One of the biggest shifts and what has triggered this survey is the desire to move away from NFRC standard size product U-values, which is what we see on NFRC/CSA labels, to a project specific size and configuration U-value. This shift is due to the acknowledgement that more accuracy is needed for fenestration as this is being used to balance other energy-efficiency items on a building.
So now, that more accurate data is being required for some projects in the upper levels of the energy codes, the question is if something needs to shift in a process in order to make this work, or can we operate as business as usual.
Well business as usual for a manufacturer to declare its thermal performance has traditionally been to provide NFRC standard size U-values at the bid and contract signing stage. But what they are not being asked to do is to provide project-specific U-values. What is missing is when should this value be calculated. Prior to bidding on a project or after being awarded a project.
So, the survey seems to imply that project-specific U-values are a design issue and not a product certification/approval issue as it has been traditionally used. And this is the major change that we all need to respect and understand.
For a supplier to perform this calculation at the shop drawing stage, once they have signed a contract stating that they will provide a certain U-value, comes with significant financial risk as the project-specific mullion and glass layout may result in a product not meeting the expected performance level. But to do this project specific caution prior to bidding on a project, means a supplier would need to factor in this overhead for each project they bid on. This will only drive up costs.
So, to address this issue, those involved need to be aware of how thermal values are calculated for fenestration and need to realize that there is no generic default value for a whole system as there is a lot of dependence on frame conductivity. But could there be…
To be able to come up with a generic value for certain products may penalize a project as window/door frames are not as simple as wood, steel and concrete structures. So, this makes no sense as a viable shift. But what about engaging with a fenestration supplier earlier? Is this the key? Well, if you consider construction services known as “pre-construction services” there is. This is where a contractor may be hired to do a cost review based on a preliminary design to determine the feasibility of a project. What if the fenestration supplier was part of this team?
As this shift will require many parties to consider doing things a bit different, I don’t have all the answers. So, this blog is about creating awareness of the issue that is being created. Energy codes will only get more complex, they don’t get easier, and this will become more important as time goes on.
If you would like some input on how some generic thermal modelling could be done, feel free to reach out to us. We provide project-specific thermal modelling on a regular basis and are more than willing to help support a design team early on in a project.