Simulations of Heat and Moisture Conditions in a Retrofit Wall Construction with Vacuum Insulation Panels

Vacuum insulation panels provide unprecedented possibilities for renovating the existing building stock in a manner that reduces the thermal losses through the building envelope. This study is focused on the implementation of VIPs （vacuum insulation panels） in energy retrofit projects with rendered outer walls. Particular emphasis is put on reducing the thermal bridges due to mechanical fasteners and at the joints of the panels. These are evaluated through a parametric study of the impact of the thermal conductivity of the joints of the panels and the adjacent insulation layer as well as the material of the fasteners. The study is carried out with 3D FEM （finite element method） simulations software. Furthermore, the moisture conditions in the construction are studied. The dynamic moisture behavior of a wall construction is modeled with a two dimensional FEM model. The long term effects of vapor diffusion are investigated in terms of accumulated moisture and the risk of condensation. The results illustrate that vacuum insulation on the outside of the wall construction does not pose a moisture problem to the construction. The simulations are based on a draft of a new technical solution for the refurbishment of a building that is typical for the great Swedish building program of the 1970s.

A new method of rapid quality detection of vacuum insulation panels

A new method of measuring gas pressure in vacuum insulation panels(VIPs)is reported in this study,which provides a fast and efficient quality control option of production.Although there are different methods of measuring gas pressure for VIPs,connecting an internal measurement gauge to external data acquisition units is problematic.The thin high barrier film covering the panel’s core usually prevents external electrical wires or mechanical devices being connected to the inside of the VIPs.To solve this problem,a micro capacitive pressure sensor with 0 to 250 Pa detection range is developed to detect the vacuum pressure.The sensor has high linearity and a sensitivity of 10 mV/Pa.Moreover,through the communication mode study,an ultrasound communications system for VIPs is designed.It shows from operation that this system is stable and reliable,and quick for communication speed.This new method enables the quality detection of VIPs to be completed within 1 second.The minimum detectable pressure of VIPs is below 1 Pa,and the measurement error can be controlled around 5%.

POWER CONSUMPTION COMPARISON OF FIVE BUILDING ENVELOPES IN THE NORTHERN PRAIRIE CLIMATE OF MANITOBA

The energy efficiency of a building depends on building envelope performance.The results presented in this paper are the first of a long-term building envelope research project at the Alternative Village at the University of Manitoba in Winnipeg,Manitoba,Canada.Five test buildings were constructed using the following systems:two wood frames with fiberglass batt insulation and dense pack cellulose,one polyurethane structural insulated panels(PUR SIP),and two with the Stay in place PVC concrete form building system using 102mm and 204mm of concrete externally insulated with 102mm of expanded polystyrene foam.All of the buildings had a common foundation and roof system with a footprint of 23.8 m2.Blower door tests were conducted to determine air tightness.Each structure was heated with an electrical resistance heater and maintained at a constant internal temperature.The thermal gradient through the wall and power consumption were monitored.The study period discussed in this report represents the main heating season from October 2011 to April 2012 consisting of 209 days.Based on the power consumption,the PUR SIP consumed the least at 2498 kWh,while the 204 mm Stay in place PVC concrete form building used the most at 2898 kWh for the same time period.The thermal gradient through the cross section of the wood frame structures was compared through the cavity insulation and at the stud.It was found that the cellulose building provided better thermal resistance along the stud when compared to the fiberglass batt insulation.

MOISTURE AND FLEXURAL BEHAVIOUR OF HEMP MAT FOAM STRUCTURAL INSULATED PANEL SPECIMENS

The use of structural insulated panels(SIPs)for wall and roof assemblies in residential and commercial buildings is a well-known construction technique.SIPs typically use a combination of either expanded polystyrene foam(EPS)or polyurethane foam(PUR)as the core material.The covering or skin is predominantly oriented strand board(OSB).The OSB is either bonded to the foam with adhesive in the case of EPS,while polyurethane is used to provide adhesion with PUR SIPs.This paper presents the results of research that investigated the use of industrial hemp mat used as a skin for soy-based polyurethane foam panels.A series of tests were conducted to investigate moisture resistance and flexural behaviour on hemp mat foam panels.Moisture absorption behaviour was evaluated on three specimen types:uncoated,earth plaster and tung oil treated hemp mat.The absorption coefficient Aw was determined for all specimens.The tung oil treated specimens exhibited a water absorption coefficient that was 5.3%of that for untreated hemp mat panel specimens.Flexural tests were conducted on dry specimens with earth-plastered hemp mat,tung oil coated hemp mat,OSB and,untreated hemp mat skins.Tung oil provided resistance to tension failure and increased capacity to withstand considerable deformation without tensile failure in flexural specimens.Compared with pure foam specimens,untreated hemp mat improved flexural performance by 16.3%.

A Method to Measure Thermal Conductivity of Vacuum Insulation Panel Using Enhanced Extreme Learning Machine Model

Thermal conductivity is an important quantity which represents the characteristic of Vacuum Insulation Panel’s(VIP’s)performance.Precise measurement of thermal conductivity provides better quality assurance for the users.In this paper,we presented a novel embedded sensor method to measure the thermal conductivity of VIP.The proposed method evaluated the quality of VIP primarily based on the relationship between thermal conductivity and frequency characteristic of the output signal.In addition,we presented a new mean ridge regression extreme leaning machine(M-RRELM)model via improving extreme learning machine(ELM)by ridge regression to modify the relationship between the thermal conductivity and the output signal frequency characteristic.Experiments have shown that the M-RRELM model has higher precision compared with the traditional ELM.The proposed method achieved good performance and was faster than the well known methods.

The development of ultralightweight expanded perlite-based thermal insulation panel using alkali activator solution

The International Energy Agency(IEA)states that global energy consumption will increase by 53%by 2030.Turkey has 70%of the world’s perlite reserves,and in order to reduce energy consumption a thermal insulation panel was developed in Turkey using different particle sizes of expanded perlite(EP).In this study,0–1.18 mm(powder)and 0–3 mm(granular)EP particle sizes were selected,since they have the lowest thermal conductivity coefficients among all the particle sizes.In addition,an alkali activator solution was used as a binder in the mixtures.The alkaline activator solution was obtained by mixing sodium hydroxide solution(6,8,10,and 12 mol·L−1)and sodium silicate(Module 3)at the different ratios of Na2SiO3 to NaOH of 1,1.5,2,and 2.5.This study aimed to experimentally determine the optimum binder and distribution ratio of EP,with the lowest coefficient of thermal conductivity and the lowest density.The lowest thermal conductivity and the lowest density were determined as 0.04919 W·m−1·K−1 and 133.267 kg/m3,respectively,in the sample prepared with 83.33%powder-size EP,6 mol·L−1 sodium hydroxide solution,and ratio of Na2SiO3 to NaOH of 1.5.The density,thermal conductivity,and compressive strength of the sample showed the same trends of behavior when the Na2SiO3 to NaOH ratio was increased.In addition,the highest compressive strength was measured in 12 mol·L−1 NaOH concentration regardless of particle size.In conclusion,the study predicts that the EP-based thermal insulation panel can be used as an insulation material in the construction industry according to the TS825 Thermal Insulation Standard.