Hello,
Looking for additional clarification on on modeling HM doors on the perimeter of the building. The opaque doors are not labelled and therefore considering to use the following U-factor value from A7.1: "Insulated metal swinging doors, including fire-rated doors, insulated access hatches, and insulated smoke vents: 0.50"
1) Installer provided a certificate stating that with 1.75 inch thickness for the unlabelled HM doors with R-26 Rockwool insulation inserted under the hats and between the ribs of internal steel stiffeners, it's U-0.13. Is there any additional information should be asking them to support this claim, so I don't have to default to using the 0.50 U-factor per Appendix A7.1?
2) There is a variety of HM door types from Corridors leading to MECH rooms and bathroom, that I intend to model. These HM doors have features such as "kick plates with louvers". Is it necessary to model these interior doors considering temperature differential in these spaces?
Thank you in advance.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
October 1, 2019 - 4:53 pm
U0.13 sounds like a point calcualtion. U0.5 sounds much more reasonable and realistic for an overall value.
You don't need to model the interior doors, especially if the spaces are adiabatic.
Fatou Jabbie, | Technology | Design and Engineering Plan Reviews | Energy Code Compliance | Sustainability | LEED AP BD+C
Founder and PrincipalUSL Technology Inc.
3 thumbs up
October 1, 2019 - 7:31 pm
Marcus,
Thank you for your feedback. especially on the interior doors as well.
Regarding the U0.13 sounding like a point calcualtion, can you elaborate on that? Am assuming you meant that, the calls might be aiming to get LEED points rather than accurately reflecting of the true U-Factor value?
I just want to make sure I understand so I can provide the right supporting documentation when required. When I created the door hallow meter assembly with the insulation in my energy model, the software is showing a close U-Facotor the supplier provided as well. Would it make sense to go with the .13? If not, how do I true up the model to the .50 U-factour?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
October 2, 2019 - 11:30 am
Point calculation is using a single point on the door or wall assembly to calculate the U value. With a door there is a the hollow part with insulation and the framing around the perimeter. Obviously the U-value is very different if determined at a point in either area. So it is the whole door assembly U-value which is important. This is a sort of weighted average of the area of differing U-value. When using manufacturer provided data it is critically important to understand how they derived the U-values they provide.
Fatou Jabbie, | Technology | Design and Engineering Plan Reviews | Energy Code Compliance | Sustainability | LEED AP BD+C
Founder and PrincipalUSL Technology Inc.
3 thumbs up
October 2, 2019 - 1:32 pm
Well said, thank you for the additional clarification.
I just followed up with the manufacturer, and what they are saying is that the U-factor for the 1.75 inch thickness is dependent on the coefficient on both outer surfaces. And using the ASHRAE Fundamental Handbook 1997 chapter 24.10, they used the K-Value of 1.63 for the air film coefficient, this value is a vertical surface exposed to essentially still air (interior). With R-26 insulation, they used a K-Value of 0.26. Overall, using these values for the door composite, they derived the U-factor of 0.31.
Does this make sense since they took the coefficient on both outer surfaces?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5868 thumbs up
October 2, 2019 - 2:50 pm
Makes more sense that U0.13. Sounds like U0.31 is possible. The films are applied to the interior and exterior surfaces but they are usually different, not the same.
Fatou Jabbie, | Technology | Design and Engineering Plan Reviews | Energy Code Compliance | Sustainability | LEED AP BD+C
Founder and PrincipalUSL Technology Inc.
3 thumbs up
October 2, 2019 - 3:00 pm
Sounds good. Will use U-0.13 and will submit manufacturer provided certificate. Thank you for all your help!