Thermal response of basement wall systems with low-emissivity material and furred airspace

Abstract

http://www.nrc-cnrc.gc.ca/ircThe material in this document is covered by the provisions of the Copyright Act, by Canadian laws, policies, regulations and international agreements. Such provisions serve to identify the information source and, in specific instances, to prohibit reproduction of materials without written permission. For more information visit http://laws.justice.gc.ca/en/showtdm/cs/C-42Les renseignements dans ce document sont protégés par la Loi sur le droit d'auteur, par les lois, les politiques et les règlements du Canada et des accords internationaux. Ces dispositions permettent d'identifier la source de l'information et, dans certains cas, d'interdire la copie de documents sans permission écrite. Pour obtenir de plus amples renseignements : http://lois.justice.gc.ca/fr/showtdm/cs/C-42 In basement wall systems, airspaces can contribute in obtaining a higher thermal resistance, if a low emissivity material such as reflective foil is installed within a furredairspace. In this study, numerical simulations were conducted using the hygrothermal model "hygiRC-C" that was developed at the National Research Council of Canada's Institute for Research in Construction (NRC-IRC) to investigate the steady-state and transient thermal performance of basement wall systems.This model solves simultaneously the energy equation in the various material layers, surface-to-surface radiation equation in the Furred-Airspace Assembly (FAA) , Navier-Stokes equation for the airspace, and Darcy and Brinkman equations for the porous material layers. The wall systems used in the simulations incorporate a low emissivity material (foil with emissivity = 0.04) bonded to a moulded/expanded polystyrene (EPS) foam that is installed in a furred-airspace assembly. The furring is installed horizontally and covered with a gypsum board. The structural element of the wall (external layer) is a poured-inplace concrete. Walls with and without FAA were considered in this study. Also, consideration was given to investigate the effect of the above-grade and below-grade portions of the wall on the thermal performance when these walls are subjected to two different Canadian climates. Results showed that at steady state condition, the effective thermal resistance (R-value) of the wall with a FAA depends on the soil, outdoor and indoor temperatures. Additionally, these wall configurations resulted in an energy savings of -17% compared to walls without FAA when these walls are subjected to two different climate conditions.

Practical correlations for the thermal resistance of vertical enclosed airspaces for building applications

“…For example, in Figure 10b for an enclosed airspace having a thickness of 13 mm (T avg = 10.0 o C, T = 16.7 o C), it is shown that increasing H from 8 in (203.2 mm) (A R = 16) to 88 in (2,235.2 mm) (A R = 172) resulted in an increase in the R-value by 20.3% at  eff = 0.03. This observation is in agreement with results from previous studies [7,9].…”

“…For an enclosed airspace of  = 13 mm (H = 12 in (304.8 mm)) and for the "1-Cavity" case, Figure 6 shows that the predicted R-values are in good agreement with R-values of the ASHRAE table for In recent studies [7,9], the contribution of Furred-Airspace Assembly (FAA) to the R-values of wall systems with horizontal furring and vertical furring of the same center-to-center spacing were investigated. The FAA was attached to EPS layer (1 in (25.4 mm) thick), which was bonded by Low Emissivity Material (LEM) facing the airspace (1 in (25.4 mm) thick).…”

“…The FAA was attached to EPS layer (1 in (25.4 mm) thick), which was bonded by Low Emissivity Material (LEM) facing the airspace (1 in (25.4 mm) thick). The results from these studies [7,9] showed that the contribution of FAA to the R-value of a wall with vertical furring was greater than that for a wall with horizontal furring. Note that the height of the enclosed airspace in the wall with vertical furring was greater than that in the wall with horizontal furring.…”

Practical correlation for thermal resistance of low-sloped enclosed airspaces with downward heat flow for building applications

“…Many studies were conducted to determine the R-values of RI products, and wall and roofing systems incorporating RI products (Yarbrough 1983, Fairey 1985, Han et al 1986, Desjarlais and Tye 1990, Desjarlais and Yarbrough 1991, Medina 2000, Al-Homoud 2005, European Commission 2010, Saber and Swinton 2010, Craven and Garber-Slaght 2011, Saber et al 2011b,c, Vrachopoulos et al 2012, D'Orazio et al 2012, Saber and Maref 2012,b,c, Escudero et al 2013, Tenpierik and Hasselaar 2013, Saber 2013a.…”

Energy retrofit using vacuum insulation panels: An alternative solution for enhancing the thermal performance of wood-frame walls

“…The present model was also benchmarked against GHB test results [24] and then used to conduct numerical simulations to investigate the effect of foil emissivity on the effective thermal resistance of different wall systems with foil bonded to different types of thermal insulations placed in furred-airspace assemblies, in which the foil was adjacent to the airspace [20,23,26]. Recently, this model was benchmarked against the test data of different types of reflective insulations [28][29] that were obtained using the ASTM C-518 test method, and then used to examine the thermal performance of different types of reflective insulation assemblies.…”