More windows fell from high-rise homes in the first five months of this year compared to the same time last year.
From January to May, there were 27 cases, according to the Building and Construction Authority's (BCA) records.
This compares to 18 in the first five months of last year, and 43 for the whole of that year.
On this year's numbers, National Development Minister Khaw Boon Wan said: "While there were no injuries, we were simply lucky. The next case of fallen window may not be so."
He was posting on the ministry's blog on Thursday night, ahead of one of two annual window safety days yesterday.
The other is on Dec 12. The two days were designated in 2009 to remind homeowners to check and maintain their windows at least twice a year.
The main cause of falling windows is corroded aluminium rivets that have not been replaced.
This is why, since 2000, casement windows provided by HDB come with stainless steel rivets.
And since 2004, homeowners have been required by law to replace aluminium rivets in old windows with stainless steel ones.
Those who fail to do so within five years of window installation could be fined up to $5,000 and jailed up to six years.
Yet even now, renovation contractor A Acme Design still gets several clients a month who need to retrofit their windows, said owner Edward Seow.
Besides replacing rivets, this could involve adding safety devices such as stoppers or angle strips to sliding windows, to prevent panels from slipping off the track. "Sometimes the older homeowners don't know that they have to retrofit," added Mr Seow.
Simply having the right parts is not enough. The authorities recommend that homeowners clean and lubricate the moveable parts of windows at least twice a year.
Old parts should also be replaced if they have been damaged by wear and tear.
"Even if the rivets are okay, after some time, the friction stay will loosen over time," said C & G Aluminium And Renovation owner Lim Seng Chuan, referring to the flat hinges that hold windows in place when they are open.
If a window falls due to lack of maintenance, homeowners could face a fine of up to $10,000, a jail term of up to a year, or both.