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title: FAQ | BuildingGT
description: Explore UVAL Wired and Wireless Systems for accurate U-Value measurements. Download the brochure for detailed insights and book a meeting with our expert today.
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##### [ UVAL Wireless Explore our wireless system for accurate and remote U-Value measurement.](https://info.greenteg.com/building/uval-wireless?hsLang=en)
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##### [UVAL Wired vs UVAL Wireless Discover the key differences between our two U-value measurement systems.](https://info.greenteg.com/building/uval-wired-vs-uval-wireless?hsLang=en)
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ABOUT
# Frequently Asked Questions
### General Product Questions
###### What are the key differences between the Wired and Wireless system?
- UVAL Wireless supports up to 5 measurement points per system, offering greater flexibility in data collection. UVAL Wired only supports one U-value measurement.
- UVAL Wireless allows for remote monitoring. This enhances convenience and efficiency. Our Wired system requires direct access to the site to receive data recordings.
- UVAL Wireless provides direct measurements for U-Value, R-Value, and Lambda Value. UVAL Wired provides only U-Value measurements; you would need to calculate the R-Value separately.
- UVAL Wireless is an expandable system, meaning you can purchase more measurement points over time. UVAL Wired is not expandable.
###### Do I need remote access to use the UVAL Wireless System?
- No. The system works locally.
- The Remote Measurement Access add-on is only for remote viewing/management (1-year free trial, then CHF 199/year).
- For UVAL Wired, no remote access is available.
###### What countries are the systems available in?
- Customers worldwide can purchase and use our UVAL Wired System.
- UVAL Wireless is only available in Europe, most of Africa, and the Middle East. This is because it employs a sub-GHz Communication link at 868 MHz.\*
*\*If you are interested in our UVAL Wireless system and you are located outside of Europe, please reach out to us and we can evaluate a customized option.*
###### What is the operating principle of the UVAL Wireless System?
The nodes communicate to the base station, which stores all the data. Nodes only transmit data when someone plugs a sensor into them. When you’re not taking measurements, please disconnect the sensors.
The nodes communicate to the base station on a specific subGHz frequency.
###### Can I unplug my UVAL Wireless base station?
Connect the base station to a power source during measurement, as its battery life is 48 hours. ISO 9869 compliancy requires a minimum measurement period of 72 hours.
###### What are the warranty terms?
- 12-month limited warranty for materials/workmanship when used correctly.
- Please report any defects within 14 days of discovery.
###### Is the software included?
- Yes, the software is included in your purchase.
- For remote access via the cloud, the software is available through a 1 year trial, and afterwards costs CHF 199 per year.
###### What happens when the node battery dies?
Node batteries last 2 years. The batteries can be replaced easily on the market for less than 10 CHF. We are also happy to replace these if preferred.
### Measurement Method & Accuracy
###### Which standard does UVAL follow?
ISO 9869-1 (heat-flow meter method) for in-situ thermal resistance/transmittance.
###### How long should I measure U-value for?
Plan for ≥72–96 hours with ΔT ≥ 5 °C between inside and outside. The longer the better if ΔT is small or the environment is unstable.
###### Do you account for dynamic or storage effects?
Indirectly, ISO 9869 uses multi-day windows (multiples of 24 h) and stability checks (compare first vs. last 24 h), so transient effects average out.
###### How do you compute U-Value and R-Value?
- U-value: (U = q / \\Delta T) (W·m⁻²·K⁻¹)
- R-value: (R = 1/U) (m²·K·W⁻¹)
###### What temperature conditions should be considered?
There should be a minimum difference of 5°C between exterior and interior environments. This requirement can make conducting summer measurements more challenging.
###### What standards must I comply with for an accurate measurement?
Data collection, analysis, and reporting per ISO 9869-1 (heat-flow meter method).
### Sensor Mounting & Environment
###### Can I measure a wall near a window?
- Yes. Make sure to keep ≥ 3× wall thickness from the window edge to avoid any potential edge effects (e.g., 30 cm wall → ≥ 90 cm away).
- Place the outside temperature probe so it reflects the cavity air, often close to the ambient sensor. Positioning this on the outermost layer is fine.
###### How do humidity and condensation affect U-value?
U-value is defined for dry heat transfer. It is best to avoid evaporation/condensation. Ensure the air dew point is below the coldest air temperature in your setup.
###### Do you have any recommendations for sun, rain, or snow?
- Often, north-facing surfaces are preferred in order to reduce solar effects. It is a good idea to avoid direct sunlight for U-value measurements.
- In rain or snow conditions, place each node in a vented plastic bag (e.g., Ziploc) so cables exit and protect electronics while allowing ventilation.
###### Which building envelopes are most commonly measured on?
- Our U-Value measurement systems can record measurements on most building envelopes.
- Vented cavities do not support accurate in-situ U-Value measurements.
###### What conditions should I be wary of?
Outside:
- Avoid direct sunlight
- Protect from large rainfall.
- greenteg’s node and outdoor sensors are rated IP67.
Inside:
- Ensure the room is not occupied.
- Avoid heaters, drafts, and mold presence.
###### Tape vs. Thermal putty: Which do you recommend?
- Use double-sided tape whenever possible.
- Use putty only on very rough/uneven surfaces where tape can’t achieve contact.
- It is recommended not to combine tape + putty on smooth surfaces.
###### How many sensors and readings do I get for the UVAL Wireless Kit?
- Both the inside and outside sets receive one node, and two sensors.
- The inside set receives 3 readings (heat flux, surface temperature and ambient temperature).
- The outside set receives 2 readings (surface temperature and ambient temperature).
### Special U-Value Applications
###### Can I measure thermal bridges (e.g., concrete lintels)?
You can, but please interpret with care:
- Sensor active area: 10×10 mm; overall footprint: 30×30 mm.
- Keep ≥ 3× wall thickness from edges/heterogeneities.
- Small or narrow bridges distort local heat flow. It is worth considering multiple points and/or overlay.
###### Can I measure the U-value of glass?
Yes, with proper ΔT and stable boundary conditions.
###### Is a vented cavity suitable for U-value?
Not for true U-value of the element alone as the airflow complicates heat transfer. It is recommended to use inner-side measurements and document boundary conditions if unavoidable.
###### Can I measure U-Value on a window?
- Yes, it is possible to measure U-Value on a window. It is important to note that window measurements should only utilize nighttime data.
- Window measurements are not ISO compliant. Only nighttime readings are accurate, therefore you would not fulfil the 72-hour consecutive measurement period.
###### What exterior building conditions should I watch out for?
Direct sunlight should be avoided on the sensors. greenteg’s node and outdoor sensors are rated IP67.
###### What's the minimum period for an ISO calculation?
72 hours is the minimum ISO 9869 measurement requirement, however ideally you need at least 96 hours.
###### Do you support acoustic/noise transmission measurements?
No. Both UVAL Wired and UVAL Wireless support thermal measurements only. All other UVAL-related sensors also support thermal measurements only.
### Have more questions?
Didn't find the answers you were looking for? Reach out to us through our contact us page with your questions, and a member of our team will get back to you as soon as possible.
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