What is ASHRAE 90.1standard

ASHRAE 90.1 – Energy Standard for Buildings Except Low-Rise Residential Buildings.

 

ASHRAE 90.1

ASHRAE 90.1 (Energy Standard for Buildings Except Low-Rise Residential Buildings) is a US standard that provides minimum requirements for energy efficient designs for buildings. These include the building envelope’s thermal and air permeance performance.

The original standard, ASHRAE 90, was published in 1975.  There have been multiple editions to it since. In 1999, the Board of Directors for ASHRAE voted to place the standard on continuous maintenance, based on rapid changes in energy technology and energy prices. This allows it to be updated multiple times in a year. The standard was re-named ASHRAE 90.1 in 2001. It has since been updated in 2004, 2007, 2010, and 2013 to reflect newer and more efficient technologies.

How are building components certified ?

A proposed building design is demonstrated through building energy simulation to use less energy than a baseline building built to ASHRAE 90.1 specifications. All building components must be qualified by individual testing.  Gridworx worked closely with  Simpson Gumpertz & Heger, an independent engineering firm, in the development of this system. It was deemed to meet or exceed performance standards in Thermal Performance, Air Barrier Performance and Condensation Potential. View a complete summary of this analysis click here.

Structural analysis of the stone and anchoring methods and patented lineal aluminum extrusions where conducted by Architectural Wall Systems, Inc and verified that our system can perform to ASHRAE specified criteria.

View a complete summary of this analysis click here.

Hows the Weather Where You Are?

ASHRAE zone mapWe asked  to Simpson Gumpertz & Heger, to perform a series of thermal analyses of the “Gridworx” mechanical stone hanging system to determine the specific detailing and insulation thickness necessary to meet the prescriptive thermal performance requirements for exterior walls contained in ASHRAE  90.1 – Energy Standard for Buildings Except Low-Rise Residential Buildings. Findings from their study are presented in a 2013 report here. This analysis was based on commercial buildings (defined in ASHRAE 90.1 as buildings greater than three stories in height) with non-residential occupancy.
The prescriptive requirements for exterior walls in Zones 1 – 8 are presented here.

DOE Climate Zone U-value – Steel Framed U-value – CMU (“mass wall”)
Backup
1 0.124 0.580
2 0.084 0.151
3 0.077 0.123
4 0.064 0.104
5 0.055 0.09
6 0.049 0.08
7&8 NA NA

For the Gridworx system modeled with the CMU backup wall, all components are the same with the exception of the backup wall, which in this case is 8 in. thick CMU in lieu of 5/8 in. gypsum sheathing/wallboard installed over 6 in. steel studs.

SG&H calculated the U-factors for each wall system variant as described in our original report. Since all of the systems that they reviewed had the insulation fully outboard of the vapor barrier, a hygrothermal analysis was not necessary for this investigation. In this configuration, based on their experience and the results of our previous moisture migration analysis (described in the original report), the vapor barrier is on the warm-in-winter side of the insulation for cold climates which prevents condensation, and in warm/humid climates is located in the drainage cavity for the wall where condensation is not detrimental to the wall assembly since the vapor barrier also functions as a waterproofing system. This means that the exterior wall assembly described above can be used without modification in all climate zones, so long as the minimum insulation requirements described below (Tables 2 and 3) are met.

For the Gridworx system modele with the CMU backup wall, all components are the same with the exception of the backup wall, which in this case is 8 in. thick CMU in lieu of 5/8 in. gypsum sheathing/wallboard installed over 6 in. steel studs. SG&H provide the results of our thermal simulations in Table 2 for the steel framed models, and Table 3 for the cases with CMU backup wall (assuming 8 in. thick CMU, with every third core grouted). SG&H  modeled several different cases of varying insulation types and thicknesses but only present here the most simplified (i.e., with the least insulation) systems which meet the maximum ASHRAE U-value requirements for zones 1-8.

Table 2: Results of Thermal Models with Steel Framing
Maximum DOE
Climate Zone
Exterior Insulation
Type
Insulation
Thickness
(in.)
Gridworx U-Value Achieved
(Btu/h*ft2 *°F)
U-Value
Required
(Btu/h*ft2 *°F)
1 Dow Thermax 1 0.095 ≤0.124
Dow CavityMate (XPS) 1 0.105
Roxul CavityRock DD 2 0.087
2 Dow Thermax 2 0.78 ≤0.084
Dow CavityMate (XPS) 2 0.078
Roxul CavityRock DD 3 0.070
3 Dow Thermax 3 0.056 ≤0.077
Dow CavityMate (XPS) 3 0.064
Roxul CavityRock DD 3 0.070
4 Dow Thermax 3 0.056 ≤0.064
Dow CavityMate (XPS) 3 0.064
Roxul CavityRock DD 3 0.064
5 Dow Thermax 4 0.044 ≤0.055
Dow CavityMate (XPS) 5 0.055
Roxul CavityRock DD 4
6 Dow Thermax 4 0.044 ≤0.049
Dow CavityMate (XPS) 5
Roxul CavityRock DD

In all but four cases (indicated with “–“), the GRIDWORX system with the 16in. horizontal clip spacing will meet the requirements of ASHRAE 90.1-2013 in Climate zones 1-6 with exterior insulation only using 3 in. discrete z-clips to create a 4 in. deep wall cavity.

The steel-framed system, based on both the Gridworx detail regarding the effects of continuous vs. discrete vertical anchors at metal stud locations, was modeled with the following composition, from exterior to interior. For these models, no insulation was included between the metal studs.

Table 3: Results of Thermal Models with CMU Backup Wall 32 in. o.c.
Maximum DOE
Climate Zone
Exterior InsulationType InsulationThickness
(in.)
Gridworx U-Value
Achieved
(Btu/h*ft2 *°F)
U-Value
Required
(Btu/h*ft2 *°F)
1 Dow Thermax 1 0.089 ≤ 0.124
Dow CavityMate (XPS) 1 0.100
Roxul CavityRock DD 1 0.110
2 Dow Thermax 2 0.061  ≤0.084
Dow CavityMate (XPS) 2 0.070
Roxul CavityRock DD 2 0.080
3 Dow Thermax 2 0.061 ≤ 0.077
Dow CavityMate (XPS) 2 0.070
Roxul CavityRock DD 3 0.062
4 Dow Thermax 3 0.061 ≤0.064
Dow CavityMate (XPS) 3 0.056
Roxul CavityRock DD 3 0.062
5 Dow Thermax 3  0.050 ≤0.055
Dow CavityMate (XPS) 3 0.049
Roxul CavityRock DD 4  0.054
6 Dow Thermax 4 0.042 ≤0.049
Dow CavityMate (XPS) 4 0.049
Roxul CavityRock DD 5 0.048
  • 1-1/4 in. thick stone panels. Panels are hung from continuous horizontal “Gridworx”
    anchors, which are in turn attached to continuous vertical framing members.
  • 1 in. air gap.
  • Varying levels of insulation in the drainage plane installed between discrete, 4 in. tall aluminum “Z” clips spaced 24 in. o.c. The vertical framing noted above connects directly to these discrete clips. The systems were modeled using three different insulation types:
    • “Thermax” polyisocyanurate insulation by Dow; R-value 6.5/in.
    • “CavityMate” extruded polystyrene by Dow; R-value 5.0/in.
    • “CavityRock DD” mineral wool insulation by Roxul; R-value 4.3/in.
  • Bituminous self-adhered sheet membrane air/water/vapor barrier (Grace Construction Products Perm-A-Barrier or equivalent).
  • 5/8 in. exterior gypsum sheathing (Georgia Pacific DensGlass Gold).
  • 6 in. steel studs. We assumed 16 ga studs at spacing of 16 in. o.c. No insulation is included between the studs.
  • 5/8 in. interior gypsum wallboard.

A sample composition of this system can be found in Figure 1.

The U-factors calculated for each wall system variant as described in our original report.
Since all of the systems had the insulation fully outboard of the vapor barrier, a hygrothermal analysis was not necessary for this investigation. In this configuration, based on experience and the results of previous moisture migration analysis (described in the original report), the vapor barrier is on the warm-in-winter side of the insulation for cold climates which prevents condensation, and in warm/humid climates is located in the drainage cavity for the wall where condensation is not detrimental to the wall assembly since the vapor barrier also functions as a waterproofing system. This means that the exterior wall assembly described here can be used without modification in all climate zones, so long as the minimum insulation requirements described herein (Tables 2 and 3) are met.

For the Gridworx system modeled with the CMU backup wall, all components are the same with the exception of the backup wall, which in this case is 8 in. thick CMU in lieu of 5/8 in. gypsum sheathing/wallboard installed over 6 in. steel studs.

sghtestfig1
Gridworx Stone Hanging System – Steel-framed backup wall with continuous vertical Z-channels (1) and discrete Z-clips (2) supporting horizontal patented Gridworks extrusions (3)