Outdoor WBGT monitoring station with large water tank and cloud service

Related instruments Thermal comfort & microclimate, Wireless & web data loggers

Shown below is an HD35EDWWBGT outdoor WBGT monitoring station with a large water tank and cloud service.

Data logger and WBGT probes
Base unit with 4G connectivity

The features include:

  • Meets MOM workplace WBGT monitoring requirements
  • Safe for outdoor installations, with solar radiation shield for the temperature probe
  • Large water tank (500 cc), with expected autonomy longer than 1 month in Singapore
  • Data logger is battery power, with 2-year typical life
  • Base unit is with 4G connectivity and supporting cloud reading (note: local 4G subscription required, 230 VAC power supply required, base unit cannot be exposed to rain)

Shown below are the software and cloud portal screenshots:

Shown below is a photo taken from a site:

Related instruments

Thermal conductivity of 90° rotated mineral wool material

Related services Thermal conductivity

We noticed that some customers provided us with samples with 90° rotated mineral wool insulation material. Shown below is an example. The mineral wool material was rotated by 90°. The test result is significantly higher than the typical thermal conductivity of mineral wool materials. The reasons are explained in this post.

As shown in the sketch below. the mineral wool fibers are aligned in a layered structure.

  • In the normal installation, the heat flow direction is perpendicular to the layered structure. The thermal resistance is greater and the thermal conductivity is lower.
  • In the 90° rotated installation, the heat flow direction is parallel to the layered structure. The thermal resistance is smaller and the thermal conductivity is greater.

A comparison is presented in this page. In this study, the thermal conductivity is 39% higher when the mineral wool material is 90° rotated.

Diffuse daylight reflectance of glasses

Related services Glass optical & thermal properties, Daylight reflectance

As discussed in the glass daylight reflectance page, the diffuse daylight reflectance of a glass is negligible, with the following two relationships:

Diffuse daylight reflectance = 0
Total daylight reflectance = Specular daylight reflectance

In the test report, we will report the glass daylight reflectance only. Below is an example:

There is only 1 result, without the separate total/diffuse/specular reflectance components.

If the result above is expressed in the conventional total/diffuse/specular daylight reflectance format, it would be:

  • Total daylight reflectance = 0.088 (8.8%)
  • Diffuse daylight reflectance = 0.000 (0.0%)
  • Specular daylight reflectance = 0.088 (8.8%)

The diffuse daylight reflectance is negligible, but not exactly 0. It is related to the haze level of the glass. The haze level of typical glasses is less than 0.5%. The diffuse daylight reflectance can be calculated as 0.088 × 0.005 = 0.00044 (0.044%) ≈ 0.000 (0.0%)

In practice, the instrument is not able to accurately measure (or resolve) the diffuse daylight reflectance of a glass. The test method of measuring glass diffuse reflectance is also not defined in the standards.

Therefore, there is only 1 result in the test report, without 3 separate components. The diffuse daylight reflectance of a glass can be estimated theoretically, but cannot the determined by an instrument.

Glass substrate for window film optical & thermal property testing

Related services Glass optical & thermal properties

For window film optical & thermal property testing, the window film must be applied onto a glass substrate, and it is not practical to test the window film as a standalone film.

If the objective is to obtain the performance data of the window film on a specific type of glass, the film needs to be applied to the known glass type for testing. The glass substrate could be a single glazing glass (e.g. a laminated glass) or a double-glazing unit (DGU).

If the objective is to generate the general performance data of a window film, the following glass substrates are recommended in NFRC 304:

  • Applied films are measured with transparent glass with a solar transmittance greater than 0.820 (Tsol > 0.820) and a visible transmittance greater than 0.890 (Tvis > 0.890).
  • Glass that meets this criterion includes 3mm clear glass, 3 mm low-iron glass, 6 mm low-iron glass.

In practice, we recommend using 3-6 mm clear or low-iron glasses as the substrate.

Substrate for paint/coating material SRI testing

Related services Solar reflectance index (SRI)

For paint/coating materials, we cannot directly test the wet samples. The paint/coating needs to be applied onto a substrate material for testing.

For thin paint/coating layers, they are translucent to solar radiation and shown below is an example. Some solar radiation can penetrate through the thin paint/coating, reach the substrate material surface, and be reflected or absorbed by the substrate.

Example of a translucent coating layer

The substrate material has some influence on the SRI test results, though the influence is a secondary factor and weak in general.

For paint/coating on building exterior wall or roof, we recommend using cement board as the substrate, as this material is easy to obtain and is close to the plaster layer on the wall or roof.

On the other hand, due to the weak influence, it is okay to use other plate materials as the substrate (e.g. aluminium plate, gypsum board, glass plate). For typical paint/coating layers with a few hundred micrometers of thickness, the influence is close to negligible.

There is no specific requirement on the paint/coating thickness. Technically, we can test any flat surfaces, regardless of the paint/coating thickness. The manufacturer’s instructions should be followed so that the sample tested is close to the actual installed materials.

Digitally signed test reports will be issued by OTM

We are pleased to announce that digitally signed test reports will be issued by OTM, with the following benefits:

  • More secured
  • Faster delivery
  • Better image quality
  • Smaller file size

Our digital signature is auto-trusted in Adobe Reader. The signature certificate can be verified by simply clicking the signature.

During the transition period, we will still provide manually signed hardcopy reports by default. After the transition period, only the digitally signed test reports will be issued, and manually signed hardcopy reports will be provided on request only.

Glass U-value and glass tilt

Related services Glass optical & thermal properties

We were asked why the U-value of a glass is different when the glass is installed horizontally.

There are 3 heat transfer modes: conduction, convection, and radiation. The convection part is dependent on the glass tilt and it affects the glass U-value.

By default, we evaluate the U-value of a glass with the vertical tilt, which is the most common position of glasses. For a horizontally tilted glass, the U-value is significantly greater than the U-value of the same glass with the vertical tilt.

Besides the dependency on tilt, the U-value is also dependent on the glass height. Other thermal properties (e.g. SHGC) are dependent on the tilt too.

However, it does not mean that the glass U-value shall be evaluated with different tilts. There are primarily two applications:

  • Glass performance rating
  • Fenestration performance rating

For glass performance rating, it is sufficient to evaluate the glass U-value with the vertical tilt only. With this standardized tilt, fair comparisons can be performed conveniently.

For fenestration performance rating, the glass tilt is considered in the evaluation by default.