In the field of building physics, U-Value is the term used to describe the heat transfer coefficient of a building element (e.g. of a wall). The U-Value describes the insulation quality of a building. The unit of the U-Value is W/(m²K). The smaller the U-Value, the better the insulation quality of the building element.
But how to measure the U-value? Our measurement-approach uses a Heat Flux Sensor and two temperature sensors (see image below). This approach is standardized in ISO 9869, ASTM C1046 and ASTM C1155. This is the only method which delivers reliable quantitative in-situ information about a building envelope.
Read about a U-Value measurement with our gSKIN® U-Value KIT in a case study from ETH Zurich.
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To differentiate our measurement-approach from other often applied approaches we reviewed the most common ones:
- Table Look-up (Building Catalogue)/ U-Value Calculation
There are complex databases containing λ-Values of generic building elements ordered by element material and/or year of construction. With these databases, the U-value of a building envelope (e.g. wall) is calculated by adding all materials contained within the specific element (e.g. specific wall = 20cm concrete + 20cm glass wool). While this method is very simple and quick, it does not produce an accurate U-Value, only an approximation.
- Thermography (i.e. Infrared imaging)
This approach shows the thermal radiation of an object and produces an image showing spots with higher and lower radiation. It does not produce a U-Value, it just produces an image.
- Multiple Temperature Measurement
This approach is based on three or more temperature measurements on both inside and outside of a building element. While this approach produces a U-Value, it needs a minimum temperature difference of 10 °C between the inside and outside to work and it is assumend that the thermal boundary resistance is constant.
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Easy to mount
You can use normal adhesive tape to fix our sensor to any wall or window.
Easy to transport
The U-value Kit can easily be carried in our transportation box.
You can review measurement protocols easily on your laptop.
If you do not need to follow ISO guidelines, you can measure U-Values in less than an hour.
A professional, easily understood software is provided
The U-Value Kit / Sensors can be applied within R&D applications to e.g. improve insulation of materials, etc.
Typical application areas include measurement of building insulation, windows, and various industry driven R&D fields.
Thermal energy enters buildings mainly from the heating system and from solar irradiation. The energy exchange between the building and the outside is focused through the roof, walls, windows, and thermal bridges e.g. balconies, into the soil, and through exchange of ambient air. Every building is a complex thermal system and to optimize these systems (for example to reduce heating costs), precise data is required.
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As the measurement set up for glass differs due its low thermal capacity to the influence of radiation for opaque materials. Our U-Value-Kit can also be easily installed to measure the U-Value of windows.
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How to measure the U-value? 6 Steps to get started
Choose an optimal measurement spot on the building element of interest.
On the inside of this spot, place the heat flux sensor, and one temperature sensor.
On the outside of this spot, place the second temperature sensor.
Connect all three sensors to the data logging unit.
Start the measurement process (via your Laptop).
Evaluate the U-value of the wall element with the software included .
Voices from customers
„The precise measurement with the gSKIN® U-Value KIT, which was developed by greenTEG according ISO 9869, is the base of our energy– and emission potential analysis – a benefit which is valued by our customers.”
– Dr. René Salzmann, Owner and Partner,www.livingwoods.net
„greenTEG’s U-Value KIT is an excellent toolset which can be used to determine the U-values of building elements with unknown thermal characteristics – we are using it for our teaching and research activities.”
– Dr. Zoltán Nagy, Architecture and Building Systems, ETH Zürich
„The U-Value Kit has helped us to a great extent in our in-situ measurements of insulation materials. We used the sensor to determine the U-Values of various wall composites.“
– Prof. W. D. Constant Louisiana State University
„The tiny greenTEG data-logger which weights almost nothing and the small sized sensors are the ideal tool for on-site measurements and experiments. We value much that not having any display nor navigation buttons the set does not attract attention nor offers any opportunity to manipulate. The light weight allows to stick it almost anywhere. Well done greenTEG!“
– Ladislav Piršel, Executive Manager, alocons spol. s r.o.
„We were able to convince ourselves that we can gain confidence by actual and accurate measurements of the insulation quality of a wall or a window with the gSKIN sensor.
For example: The owner of the object gains confidence in the planning, if it has actual and reliable data on which he or she can rely now.“
– Martial Bujard, Director, Bureau EHE SA
„Experiences from the field show that the use of theoretical values of thermal conductivity in the calculation of the capacity needs of demand-dependent heating systems is unreliable. Measurements with greenTEG’s gSKIN (R) U-value KIT enable us to determine actual values for our projects, making our calculations much more precise, resulting in a saving of material and resources.“
– G.J. Louppen, ecodynamisch Bouwen
gSKIN® U-Value Kit
R-value vs. U-value
Comparison: Heat flux vs. temperature method
Summary of ISO 9869
ISO compliant U-Value Measurement (by ETH Zurich)
U-value measurement saves cash
Measurement vs. calculation
Calculation Tool für Window U-value (Excel)
Forgeign language articles
Chinese – U值测定 节能之道
French – Coefficient de transmission thermique
Japanese – “Ｕ値”評価 ＝ 数値として評価を得る
Korean – U-Value 측정 솔루션
Korean – KIEAE Journal
Russian – U-value
Spanish – Determinación del Valor-U – L calidad-precio
Swedish – U-värdesmätning – valuta för pengarna!
News and Publications
- Measuring U-value of glass
- Room climate
- TH Nürnberg integrates greenTEG's sensors
- Advanced building skins conference
Measuring U-values of glass with greenTEG’s gSKIN® U-value KIT
Windows play an important role in the overall insulation of a building, as they are responsible for up to 20% of heat losses during winter. Therefore, replacing poorly insulated windows with windows of the latest standard can contribute to saving significant costs and energy. Determining which windows provide the most potential in cost savings can be a daunting task, as the U-value of windows may range from 5 W/m²K for single glazed windows to 0.7 W/m²K for triple glazed windows. Oftentimes, the exact U-value of a given is unknown as the U-Value may also deteriorate over time (e.g. by leakage).
With greenTEG’s U-value Kit, the U-value of windows can be assessed efficiently. The user now has a tool, where all the information needed for a precise cost-benefit analysis for window replacement is provided.
Thermal behavior of glass differs from that of walls and because of that, a different measurement approach is required. Measurements should be conducted approximately one hour after sunset and stopped before sunrise, to avoid the effects of solar radiation, in order for results to be conform to ISO 9869 standard. Furthermore, it requires a measurement interval over three subsequent nights and results not differing more than by 5%.
To download our full case study of a window U-value measurement click here.
In order to minimize the analytical effort of the user, greenTEG provides a template that enables ISO-conform measurements without the need of interrupting the measurement process. This excel template can be found here.
U-Value Kit for checking the Swiss room climate standard
The Swiss standard SIA 180 includes requirements for heat protection, damp-proofing and indoor climate in buildings. Amongst other necessities, it requires the use of a floor whose thermal storage capacity can be used. In a pilot project, building scientists were uncertain whether the application of an insulating flooring (for example, parquet, linoleum, etc.) would fail in complying with the limit values per SIA 180. Our U-Value Kit allows to simply and precisely check these conditions.
Measurements have shown that a flooring such as novilon / linoleum has no or only insignificant influence on the thermal performance of the floor (see diagram). In a test, the heat flux sensors of two U-Value Kits were positioned at two different locations on the floor of a building. Once on bare artificial stone flooring and once on novilon / linoleum, which was mounted on the artificial stone flooring (see sketch).
Experimental housing complex built by TH Nürnberg and its project partners
TH Nürnberg builds a housing complex to test new building materials and other methods to further reduce energy consumption. greenTEG’s heat flux sensors are integrated into the wall construction to monitor the thermal behavior of a new type of insulation material.
Reducing energy consumption with innovative technologies
The housing complex consists of eight units designed as best-practice projects to demonstrate a sustainable energy supply of living quarters according to the Plusenergy-Standard. The aim of the project is to develop new technologies and methods which will surpass the current status-quo in thermal insulation, energy generation, energy storage and energy supply. Future housing projects and smaller industry operations shall profit from this new methods and technologies.
Thermal characterization of insulation materials with heat flux sensors
One focus of the project is to test a newly developed material with a very high insulation quality. This new material is fabricated on the basis of hydrophobic silicic acid which is then filled into bricks with a high insulation quality. To measure how the new material reacts under real conditions, the researchers integrated greenTEG’s heat flux sensors directly into the bricks and will then measure the thermal behavior.
From left to right: heat flux sensor mounted on brick, brick with cables for data read-out, brick with now invisible cables in the larger wall construction.
TH Nürnberg’s press release about the project (in German) can be found here
U-value measurements made easy
greenTEG’s sensors measure the thermal energy transfer through a material. With this information the thermal behavior of a material can be characterized and based on the data improved. greenTEG also offers a complete measurement solution (gSKIN® U-Value Kit) to assess the insulation quality (U-value, aka as R-value) of a building element. The gSKIN® U-Value Kit consists of a heat flux sensor, a data logger with two temperature sensors and an analysis software.
More about greenTEG’s U-Value Kit and building technology applications can be found here.
Do you have a similar project in mind where you would like to make measurements with our sensors? Then contact us to discuss a potential collaboration!
Conference on advanced building skins in Bern
Experts from around the world visited the conference on advanced building skins in Bern, Switzerland.
greenTEG presented the U-Value Kit for the assessment of the insulation quality of building elements and received very good feedback. Thank you for all the interesting discussions!
The aim of the Conference on Advanced Building Skins is to contribute to a multidisciplinary, integrated planning approach by architects, engineers, scientists, manufacturers and the building industry to reduce energy consumption of buildings. The annual international conference attracts 600 participants from over fifty countries.
List of Energy Consultants in certain regions
You are searching for information about local Building Energy Experts? Find information here.
KFW – List of Energy Consultants
Federal Minsitry of Energy – List of Energy Efficiency Experts
Geak – List of Energy Experts
|United States of America
BPI Goldstar Contractor
|United Arab Emirates
Dubai – Green Building Consultants
|Case study: U-Value measurement saves money||greenteg.com|
|Article: Zero-energy home by exhibition partner||umweltarena.ch|
|Video: How the measure the U-value?||Youtube|
|Article: Quality of building insulation precisely measured||ccr-mag.com|
|Article: The imprtance of U-values of windows||futurebuild.com|
|Article: U-Value assessment – getting value for money||Climate Control ME|
|Upcoming book: Reference to U-Value Kit||wiley.com|
|R-value vs. U-value||greenteg.com|
greenTEG develops, manufactures, and markets thermal sensor solutions. The company was founded in 2009 as an ETH Zurich spin-off and has since built up an international customer base, coupled with a global distributor network.
greenTEG’s thermal sensors are integrated into diverse applications by customers active in markets such as laser, building technologies, medtech, automotive, processing industry, and R&D.
Contact us or our distributors and tell us about your application ideas. We will support you to find the best solution for your requirements.More information about the company and its technology can be found on their website.