Patent Application
20240301693
The invention is in the field of walls for buildings with special measures for sound insulation and fire protection.
In modular construction of multi-family buildings, it is required by the International Building Code (“IBC”) to have a minimum sound transmission class (“STC”) rating of at least 50 for sound attenuation, as well as a 1-hour fire rating, in all party walls. Sound control is important in lodging structures, multi-family apartments, condominium complexes, as well as senior living facilities or any building that includes dwelling units with shared walls.
Shared walls can mean unwanted noise from the unit next door and shared corridors can also mean less privacy. It is a challenge to get a stick-framed structure to meet both sound transmission and fire resistance ratings. For newer or remodeled multi-family housing units, building codes throughout the United States require a measure of sound privacy between dwelling units. The IBC specifies a minimum architectural design standard of privacy of 50 STC.
Commonly referred to as their acronym, SIPs, structural insulated panels are high performance building panels used in floors, walls, and roofs for residential and light commercial buildings. The panels are typically made by sandwiching a core of rigid foam insulation between two structural skins. These panels are fabricated in a factory and shipped to a construction site, where they can be assembled quickly to form a tight, efficient building envelope. Cementitious SIPs are one type of SIPs, using cement-fiber board as the structural facing material.
In SIP construction it is very difficult to achieve a STC 50 rating as well as a 1-hour fire rating without the addition of multiple layers of gypsum-based drywall and other materials. Typically, in SIP construction, sound transmission loss drops significantly in the 630 Hz range due to the configuration of the skins of the panels. “Sandwich panels” such as SIPs have a well-known problem when it comes to acoustical performance: because the various layers are adhered one to the other, at certain frequencies the composite panel enters into resonance, diminishing the acoustical damping at that frequency. This, in turn, affects that critical STC rating of the system, where code requires minimum performances for different applications. One of the critical applications is party walls between living units, where the STC rating is normally 50. This is difficult to achieve with any sandwich panel that is known in the prior art, regardless of the material composition. The way other SIP manufacturers achieve the 50 rating is by adding multiple layers of drywall/gypsum and rock wool to one side of the panel to add mass to increase the dampening effect. This is not easy to do and increases costs and installation time.
What is needed, therefore, is a building party wall assembly comprising SIPS that achieves an STC rating of at least 50, has a 1-hour fire rating, and that is faster and simpler to manufacture, and therefore more affordable than the prior art, and does not contain gypsum.
The present invention is a building party wall assembly that satisfies these needs. The building party wall assembly comprises a first SIP and a second SIP separated by an air gap. The first SIP comprises a first insulation core, a first cementitious board disposed on one side of the first core, and a second cementitious board disposed on the second side of the first core. The first and second cementitious boards have approximately the same thickness as each other. The second SIP comprises a second insulation core, a third cementitious board disposed on one side of the second core and a fourth cementitious board disposed on the other side of the second core. The third and fourth cementitious boards each have a thickness that is at least twice that of the first and second cementitious boards, or approximately twice the thickness of the first and second cementitious boards. Alternatively, two first cementitious boards are stacked on top of each other and disposed on one side of the second core, and two second cementitious boards stacked on top of each other disposed on the other side of the second core. It is important that the total thickness of the cementitious boards on the second SIP is at least twice that of the cementitious boards on the first SIP. These and other benefits, features, and advantages will be made clearer in the accompanying description, claims, and drawings.
The first SIP 102 comprises a first rigid foam insulation core 105 having a first side and a second side, a first cementitious board 104 disposed on the first side of the first rigid foam insulation core 105, and a second cementitious board 104 disposed on the second side of the first rigid foam insulation core 105. Each cementitious board 104 is preferably approximately 0.5 inches thick. As assembled, the first SIP 102 is preferably approximately 4.5 inches thick.
The second SIP 103 comprises a second rigid foam insulating core 105 having a first side and a second side, two first cementitious boards 104 stacked on top of each other along their major surfaces disposed on the first side of the second rigid foam insulating core 105, and two second cementitious boards 104 stacked on top of each other along their major surfaces disposed on the second side of the second rigid foam insulating core 105 in the configuration shown in
The rigid foam insulating cores 105 preferably comprise expanded polystyrene (“EPS”) foam. The cores 105 are also preferably approximately 3⅝, i.e. 3.625, inches thick.
The building party wall 100 also comprises a frame 106 comprising nominal 2×4 inch pieces of lumber disposed at the edges of each SIP 102 and/or 103. The SIPs can be joined edge to edge via the frames 106 as shown in
The cementitious boards 104 may also comprise Vantem boards. VANTEM a trademark of Vantem Global Inc. Vantem boards are also described in US 2017/0101343 A1 by Zheng as a plate comprising a sizing agent and two fibrous layers disposed apart from each other. US 2017/0101343 A1 is hereby incorporated by reference as if it were fully rewritten herein.
The second SIP 202 of this embodiment differs from the second SIP 103 of the first embodiment. In
The sound transmission reduction in both the first and second embodiments is due to the double thickness of the cementitious boards on the second SIP. The double thickness affects the resonance frequencies of the sound energy through the structures, thereby reducing sound transmission.
The configuration described above has been tested by an independent laboratories for sound transmission loss under ASTM E90 and for fire resistance performance under ASTM E119. In the tests, the assembly of the present invention achieved an STC rating of 53, which exceeds the required minimum 50, and a 1-hour fire rating. This achievement is made with only cementitious boards and rigid foam insulation cores of particular sizes and in a particular configuration. As such, the sizes and dimensions of the various materials are considered to be critical to its success.
The use of a building party wall assembly consisting essentially of only cementitious boards, insulation cores, and a frame in this novel configuration reduces the number of parts that are required to manufacture a building wall assembly. This helps to simplify the building process and reduce its cost. The assemblies are modular, so that assemblies can be factory-built to consistent quality standards. The result is that high-quality, affordable, and energy efficient apartment buildings and single family homes can be rapidly produced, and without the need for multiple layers of gypsum and additional materials to attain a similar sound rating or fire resistance result.
Language of degree used herein, such as the terms “approximately,” “about,” “generally,” and “substantially” as used herein represent a value, amount, or characteristic close to the stated value, amount, or characteristic that still performs a desired function or achieves a desired result. For example, the terms “approximately”, “about”. “generally,” and “substantially” may refer to an amount that is within less than 10% of, within less than 5% of, within less than % 1 of, within less than 0.1% of, and within less than 0.01% of the stated amount.
While there have been described what are at present considered to be the preferred embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.
