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U-value measurement

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.

Find out more

greenTEG's U-value measurement device gSKIN U-Value Kit

To differentiate our measurement-approach from other often applied approaches we reviewed the most common ones:

  1. 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.
  2. 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.
  3. 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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Key Features

gSKIN Heat Flux sensor mounted for U-Value measurement

Easy to mount

You can use normal adhesive tape to fix our sensor to any wall or window.

Measuring U-values with the gSKIN U-Value Kit

Easy to transport

The U-value Kit can easily be carried in our transportation box.

U-value measurement tool, real-time analysis

Real-time review

You can review measurement protocols easily on your laptop.

Short u-Value measurements with the gSKIN U-Value Kit

Short measurement

If you do not need to follow ISO guidelines, you can measure U-Values in less than an hour.

greenTEG U-value software (U-value calculator)

Easy analysis

A professional, easily understood software is provided

U-value determination or heat flux measurement in Research and Development (e.g. wearable)

Many applications

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

How to measure the U-value Step 1: Optimal measurement spot for U-value determination

Choose an optimal measurement spot on the building element of interest.

How to measure the U-value Step 2: gSKIN heat flux sensor by greenTEG AG during an U-value measurement

On the inside of this spot, place the heat flux sensor, and one temperature sensor.

How to measure the U-value Step 3: Outside U-value measurement with greenTEG's U-Value Kit

On the outside of this spot, place the second temperature sensor.

How to measure the U-value Step 4: The gSKIN U-Value Kit is a plug and play solution for U-value determination

Connect all three sensors to the data logging unit.

How to measure the U-value Step 5: Start the U-value measurement via the greenTEG software tool

Start the measurement process (via your Laptop).

How to measure the U-value Step 6: Successful U-value measurement shown in a report

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.ch
    Energy consultant Livingwoods uses greenTEG gSKIN U-Value Kit

  • „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
    ETH Zurich doing U-value measurements with greenTEG U-Value Kit

  • „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
    Louisiana State University conducts U-value calculations with greenTEG's U-Value Kit

  • „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.
    Swiss Energy Consultant uses greenTEG U-Value Measurement device the gSKIN U-Value Kit

  • „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
    Swiss Energy Consultant uses greenTEG U-Value Calculator the gSKIN U-Value Kit

  • „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
    Dutch Energy Consultant uses greenTEG U-Value Calculator the gSKIN U-Value Kit


Buy the U Value Kit, Heat-Flux Sensors and our other products online

Detailed information about the U-Value Kit is available in our online shop.

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Thermalplug SPRL

Hermesstraat 2C
B/ 1930 Zaventem
Tel: +32 (0)2 711 20 32
GSM: +32 (0)474 487 486

Alocons spol. s r.o.
Lombardiniho 22/B, 831 03  Bratislava
Zero Energy Lab
Calle Mesnadas 9
09003 Burgos
17 Claregalway Corporate Park,
Co. Galway.
H91 R85P
Tel: 0818 333355
Fax: +353 01 9011374
Omni Instruments

Mid Craigie Rd, Dundee,
Dundee City DD4, GB
+44 845 900 0601

South Survey Ltd
21 Deanfield Court
Clitheroe, Lancashire, UK
+441200 429870


TecFront Electronics Corporation
Room 2615,
Jingming Center No. 278 East Wenshui Road
Jagrat Energy & Environment Solutions
7/MB/250 Indira Gandhi Nagar,
302025 Jaipur
Sensortechnos Inc.
3-24-17 Nishiazabu Kasumi Building
4F Minato-ku
Tokyo 106-0031

Autex Inc.
16-5 Tomihisa-cho
162-0067 Toyko

R1308 Kranztechno.
388 Dunchondaero, Joongwon-gu Seongnam-city,
Gyunggi-do Korea 462-729


Electro Optical Components
5460 Skylane Blvd
Santa Rosa, CA 95403, USA
+1 707-568-1642

Middle East

WaldyTech Ltd.
27 Maskit St. P.O.Box 12011
Herzliya-Pituach 46733

You want to be our Distributor for the U-Value Kit or our other products in your region?

Contact us via email otelephone.

News and Publications

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 mayU-value_measurement on window 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).

SIA 180 Switzerland
SIA 180 Switzerland

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.

sensor-in-brick-visible brick-with-cables brick-no-cables

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!

About the conference:

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.

U-value Measurement gSKIN for zero energy building

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 U-value measurement saves mones greenteg.com
Article: Zero-energy home by exhibition partner Precise U-Value Measurement instead of U-Value calculation in the environmental arena umweltarena.ch
Video: How the measure the U-value? Youtube
Article: Quality of building insulation precisely measured Precise U-Value Measurement instead of U-Value calculation in the USA ccr-mag.com
Article: The imprtance of U-values of windows U-Value Measurement vs. U-Value calculation by greenTEG in Climate Control Middle East/ Climate control ME futurebuild.com
Article: U-Value assessment – getting value for money U-Value Measurement vs. U-Value calculation by greenTEG in Climate Control Middle East/ Climate control ME Climate Control ME
Upcoming book: Reference to U-Value Kit Energy Audits and Improvements for Commercial Buildings - Ian M. Shapirg wiley.com
R-value vs. U-value U-Value and R-value, explained by greenTEG

U-Value and R-value, explained by greenTEG



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.

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Our partnerships and recognition

BFE supported us in technical research about specific questions during the development of our technology.

We are CTI certified since 2010.

Climate KIC cooperates with greenTEG at exhibiting the gSKIN U-value Kit at Umweltarena Spreitenbach. Where a live in-situ u-value measurement is showngreenTEG's U-Value Kit is shown in a live demonstration at Umweltarena Spreitenbach

Our technology of the U-Value Kit is presented in cooperation with Climate KIC at the Umweltarena in Spreitenbach.