# Cold weather cleaning

Does anybody have any tips for cold weather roof cleaning? It’s going to be in the 20’s for the next couple days and I’d rather not reschedule if it can be done SAFELY.

Is there anything I can put on the roof to get rid of the morning frost?

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This might be too late for you but in my experience sh does not work near as well when its cold. Keep in mind that SH does freeze just like water. I was told my supplier that the freezing point is pretty close to the same as water so you might be turning that house into a popsicle if you are doing it in the 20s.

Dan, I think your supplier was misinformed.

The freezing point depression of a 12% Sodium Hypochlorite solution (which also has 9.4% salt due to the manufacturing process of chlorine) is 15.3C or 27F so the freezing point is -15.3C or 5F. So unless you are expecting sustained temperatures well below freezing (i.e. closer to 5 degrees Fahrenheit or below), then it should be safe.

The full calculation was determined from the following. 12% solution is (approximately; ignoring Trade % vs. weight % distinctions) 12 grams of sodium hypochlorite in 100 grams total. There is also 12*58.443/74.4422 = 9.42 grams of salt (from the way chlorine is produced) so that’s 100-12-9.42 = 78.58 grams water. There is 12/74.4422 = 0.1612 moles times 4 for dissociation and salt (there is sodium, hypochlorite, sodium, chloride) so 0.6448 moles solute in 78.58 grams water so in 1000 grams (1 kilogram) that is 8.2 so that times 1.86 is 15.3C = 27F.

The full calculation for bleach is determined from the following. 6% solution is (assuming weight %) is 6 grams of sodium hypochlorite in 100 grams total. There is also 6*58.443/74.4422 = 4.71 grams of salt (from the way chlorine is produced) so that’s 100-6-4.71 = 89.29 grams water. There is 6/74.4422 = 0.0806 moles times 4 for dissociation and salt (there is sodium, hypochlorite, sodium, chloride) so 0.3224 moles solute in 82.29 grams water so in 1000 grams (1 kilogram) that is 3.92 so that times 1.86 is 7.3C = 13.1F.

The freezing point depression for 6% Sodium Hypochlorite as found in Clorox Regular and most Ultra brands of bleach is 7.3C or 13.1F so the freezing point is -7.3C or 19F.

However, the effectiveness is greatly diminished at or around 40F or so I have been told by others. I would think once depression temp is matched it would be ineffective but I’m not certain. I just know it won’t freeze at 32F

FYI, there is no way I would EVER attempt to clean a roof at 20F! Even if it would work! LOL

Yea I have never looked much into it but I stopped by there this winter and asked what the freezing point was for it( this was just an employee and not the management) but his response was that is was that is was close to 32 about the same as water. I didn’t put too much merit into it because my equipment nor my chemicals ever see below freezing weather because I have a heated shop and you would never catch me out washing in close to freezing weather. I try not to wash below 50 but even in the 50s I have to wait a lot longer for my mix to work than I do in the summer. Thanks for the info though.