technical

Download the technical report HERE (10.8MB).

The five layers of the blinds are;

1. Room side fabric – 100% polyester with blackout surface, H&S fabrics ‘Waldorf’ range
2. 12mic Aluminised Mylar MET813 (space blanket)
3. 7mm C100 Thinsulate, 3M, (‘Clo’ value of circa 1.1)
4. 12mic Aluminised Mylar MET813
5. 110g cotton polyester sateen lining fabric (other choices available)

The inner layers incorporate a 7mm ‘Thinsulate’ core (a highly insulating thermal fleece, normally used for clothing), with two layers of aluminium faced Mylar (‘space blanket’ material as developed by NASA) either side of the core.

Technical performance

In December 2010 a six hour test of the blinds performance was undertaken using the prototype fitted to a typical single-glazed Victorian window. The results showed that the blinds prevent a significant heat loss through the window glass & improve the comfort levels (and downdraft) close to the window, internally. From this a guide U-Value of the blinds has been ascertained and hot-box tests are planned at the National Physics Lab (see Retrofit for the Future info). Ultimately the approximate heating cost savings and payback period for the blinds can be estimated. Download the full report HERE (10.8MB).

extracts;

Test of internal temp. impact when blind is up / down

The average outside temperature was around 3˚C & internal temperature 20˚C.

window temperatures with & without the blind

Results show;

A. With no blind in place the external temperature at 14mm from outside surface of the glass rises significantly from ambient external temperature (by about 3˚C).

B. With no blind in place temperatures just inside the glass (17mm) are generally between 6 – 10˚C warmer than ambient external, [but NB 2˚C internal temp difference between two periods]. Average temp. was 8.0˚C.

C. With no blind in place temperatures just inside the glass (17mm) are generally between 3 – 6˚C cooler than ambient internal. [Note that first ‘up’ period is relatively short]. Mean is 4.0˚C cooler.

D. With the blind in place temperatures just inside (17mm) the glass are generally between 3 – 5˚C warmer than ambient external temperature. Average 4˚C warmer.

E. With the blind in place (down), the temperature just inside the glass (17mm) was generally around 12.5˚C cooler than ambient internal temperature (20˚C). This gives an indication of the performance of the blind & from this an assumed U-Value can be calculated.

Section through blind & window showing thermometer positions