Hi Harriette, Hope it's okay I share my experience with invisible grilles. I used invisible grilles in my current house (not new house), installed them about 2 years ago and removed them a year later. I used the trademark owners, not the other one. Wasn't a good experience. I have cats so I asked the sales person who came to do a site visit for her suggestions. She said because my windows were long, it was better to use vertical grills rather than horizontal ones as it will slack near the centre. Mine is the standard HDB Punggol window, 4 leaves/panels. Then she suggested a gap of 2-inch so the cat head cannot come out. I thought she'd know best so proceeded with her suggestion. Only opted to do for windows in my living room and children's bedroom. On day of installation, the workers are Bangladeshis and their supervisor didn't come until much later when I made a complain. The process is this: for vertical grills they will drill a hole to insert a screw 2 inches apart just below your window frame so for me we have like 50-plus drill holes. Then they weave the wire grill material then put on a white frame to cover the screws. First problem: the grill lines were not straight. They were supposed to use laser pointer to create straight lines but the workers took short cut maybe? Anyway I called the supervisor to site and he agreed the lines were not straight, particularly the last 5 lines near the walls so they took it out, drilled more holes and patched the prev ones then weave the whole thing again. This time it was almost 80% straight, supervisor said last 2 lines cannot be straightened. By then we'd already moved in so each visit was a great inconvenience to me. The end product really made my house look like jail because the grills were close to one another and I have a fairly long hall compared to most other houses, even then it's very obvious. But I needed it because got cats and kids. A few months later I called the sales person to give feedback that the gaps were very tight so it was quite difficult for me to squeeze my hands through to close the windows when it rains, and after much bugging then she finally told me she recommended 2 inch instead of 3 inch because there was no stock previously. I was surprised, I thought the gaps was drilled, what does it have to do with stock? Maybe it was the frame, I don't know and didn't ask. For a few months, I lived either with completely closed windows for few weeks at a go, or completely open windows even when it rained. After a year, I cannot tahan already and I asked if we can amend and re-weave the grills to 4 inch gaps since we are using existing hardware, so just skip a screw only. Again, the sales person said no cannot be done. Not very helpful in providing options. By this time, I was getting very frustrated and asked that they remove the whole thing and patch up the holes in the wall. They charged me $200 for that. Finally did it and now I'm $1k plus poorer and back to square one.