Heat-flow variability of suspended timber ground floors: Implications for in-situ heat-flux measuring

Pelsmakers, Sofie; Fitton, Richard; Biddulph, P.; Swan, William; Croxford, Ben; Stamp, Samuel; Calboli, Federico C. F.; Shipworth, David; Lowe, Robert; Elwell, Clifford A.

doi:10.1016/j.enbuild.2016.12.051

Cited by 9 publications

(19 citation statements)

References 21 publications

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“…As expected, and as also reported for the floor of a thermal chamber (Pelsmakers et al, 2017), a large spread of U p -values was observed across the floor in this case study in the field. In general, a clear negative association exists between the measured U p -value in a location and its distance from the external perimeter wall: estimated U p -values progressively reduce with the distance from the perimeter wall (Figures 5 and 6).…”

Section: Analysis Results and Discussionsupporting

confidence: 66%

“…Figure 6 shows that there is no abrupt change after 1 m, but instead a gradual reduction in U pvalues as the distance to the external environment increases (Pelsmakers et al, 2017). It also highlights that when locations were observed in the perimeter zone but not aligned with airbricks in the void below (locations 14-16), U p -values were significantly lower than those in front of airbricks (locations 1, 2, 6-8 and 22) and generally these U p -values were outside the estimated error margins.…”

Section: Analysis Results and Discussionmentioning

confidence: 99%

“…In general, a clear negative association exists between the measured U p -value in a location and its distance from the external perimeter wall: estimated U p -values progressively reduce with the distance from the perimeter wall (Figures 5 and 6). This is caused by an increase in the thermal resistance as the distance to the exterior wall increases, while void ventilative heat flow is also lower further away from the perimeter wall airbricks and behind several sleeper wall obstructions (Pelsmakers et al, 2017). A simplified categorization of a 1 m perimeter zone was used to investigate separately estimated U p -values in non-perimeter and perimeter zones, similarly to Delsante (1989).…”

Section: Analysis Results and Discussionmentioning

confidence: 99%

“…For suspended timber ground floors, a recent study suggests that models might underestimate suspended ground-floor heat loss; however, this was based on a thermal chamber study at the Salford Energy House (Pelsmakers et al, 2017). The current paper presents the results of high-resolution in-situ measurements of a suspended timber ground floor in a pre-1919 terraced house in west London, UK.…”

Section: Introductionmentioning

confidence: 99%

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Suspended timber ground floors: measured heat loss compared with models

Pelsmakers

Croxford

Elwell

2017

Building Research & Information

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There are approximately 6.6 million dwellings in the UK built before 1919, predominantly constructed with suspended timber ground floors whose thermal performance has not been extensively investigated. The results are presented from an in-situ heat-flow measuring campaign conducted at 27 locations on a suspended timber ground floor, and the estimated whole-floor U-value compared with modelled results. Findings highlight a significant variability in heat flow, with increased heat loss near the external perimeter. In-situ measured-point U-values ranged from 0.54 ± 0.09 Wm −2 K −1 , when away from the external wall perimeter, to nearly four times as high (2.04 ± 0.21 Wm −2 K −1 ) when near the perimeter. The results highlight the fact that observing only a few measurements is likely to bias any attempts to derive a whole-floor Uvalue, which was estimated to be 1.04 ± 0.12 Wm −2 K −1 and nearly twice that derived from current models. This raises questions about the validity of using such models in housing stock models to inform retrofit decision-making and space-heating-reduction interventions. If this disparity between models and measurements exists in the wider stock, a reappraisal of the performance of suspended timber ground floors and heat-loss-reduction potential through this element will be required to support the UK's carbon-emission-reduction targets.

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Section: Analysis Results and Discussionsupporting

confidence: 66%

Section: Analysis Results and Discussionmentioning

confidence: 99%

Section: Analysis Results and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Suspended timber ground floors: measured heat loss compared with models

Pelsmakers

Croxford

Elwell

2017

Building Research & Information

Self Cite

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“…An example of this is given in a recent study carried out at the Energy House on the subject of suspended timber floors. Significant variation was found across only one room, in which is a simple ventilated timber floor [33].…”

Section: Reliability Of In-situ Measurementsmentioning

confidence: 99%

Variations in the U-Value Measurement of a Whole Dwelling Using Infrared Thermography under Controlled Conditions

et al. 2018

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U-values of building elements are often determined using point measurements, where infrared imagery may be used to identify a suitable location for these measurements. Current methods identify that surface areas exhibiting a homogeneous temperature-away from regions of thermal bridging-can be used to obtain U-values. In doing so, however, the resulting U-value is assumed to represent that entire building element, contrary to the information given by the initial infrared inspection. This can be problematic when applying these measured U-values to models for predicting energy performance. Three techniques have been used to measure the U-values of external building elements of a full-scale replica of a pre-1920s U.K. home under controlled conditions: point measurements, using heat flux meters, and two variations of infrared thermography at high and low resolutions. U-values determined from each technique were used to calibrate a model of that building and predictions of the heat transfer coefficient, annual energy consumption, and fuel cost were made. Point measurements and low-resolution infrared thermography were found to represent a relatively small proportion of the overall U-value distribution. By propagating the variation of U-values found using high-resolution thermography, the predicted heat transfer coefficient (HTC) was found to vary between 183 W/K to 235 W/K (±12%). This also led to subsequent variations in the predictions for annual energy consumption for heating (between 4923 kWh and 5481 kWh, ±11%); and in the predicted cost of that energy consumption (between £227 and £281, ±24%). This variation is indicative of the sensitivity of energy simulations to sensor placement when carrying out point measurements for U-values.

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Are the energy savings of the passive house standard reliable? A review of the as-built thermal and space heating performance of passive house dwellings from 1990 to 2018

Johnston

Siddall²,

Ottinger

et al. 2020

Energy Efficiency

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The Passive House (PH) Standard is a voluntary quality assurance standard focused upon maximising the health and wellbeing of occupants, whilst reducing space heating demand to a very low level. To meet the PH standard well defined criteria have to be met. However, given literature that suggests a 'performance gap' for energy savings, the question remains, how well do PH dwellings perform in situ?This paper presents results from in situ building fabric thermal performance measurements, along with a comparison between the design intent and the measured space heating energy used by over 2000 newly built and retrofitted PH dwellings. The results reveal the in situ thermal performance of the building fabric is close to the design predictions. Within space heating measurements, a standard deviation of up to 50 % has to be attributed to the broad spectrum of user behaviour; this is not specific for PH, but a general observation. Despite this, the average values for the PH developments ranged within the uncertainty of the demand calculations. With over 2000 PH dwellings averaging a space heating energy consumption of 14.6 kWh/(m²a), the in situ performance is close to the original design intent and extraordinary low compared to the consumption in ordinary buildings.The results suggest the PH Standard is capable of producing dwellings in a verifiable manner. This means, on average, the in situ thermal performance of the building fabric and the energy consumption for space heating match the design intent i.e. there is no significant 'performance gap'.

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Heat-flow variability of suspended timber ground floors: Implications for in-situ heat-flux measuring

Cited by 9 publications

References 21 publications

Suspended timber ground floors: measured heat loss compared with models

Suspended timber ground floors: measured heat loss compared with models

Variations in the U-Value Measurement of a Whole Dwelling Using Infrared Thermography under Controlled Conditions

Are the energy savings of the passive house standard reliable? A review of the as-built thermal and space heating performance of passive house dwellings from 1990 to 2018

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