Has anyone ever made and/or installed interior storm windows? Any advice? [View all]

I have a 1970 home with old, leaky, multi-paned, double sash wooden windows. I can't afford new windows or storm windows at this time. I need to keep cold air out. Because of my HOA association rules, I can't install DIY plastic storm windows on the outside of the windows. (I could install "store bought" storm windows" but I can't afford those right now.) I want to install the interior storm windows in the two upstairs bedrooms. There are two windows in each room. I have standard window screens on the outside of these windows. I open the windows in nice weather to let fresh air into the house. I need removable interior storm windows so that I can open the windows in case of an emergency. The pressure fit windows in the Mother Earth News DIY project that I found (see link below) seem to be a good idea.

Link to a Mother Earth News DIY project here: http://www.motherearthnews.com/do-it-yourself/storm-windows-zm0z10zhun.aspx
I think that I could make these storm windows but with screwed together frames instead of the fancy joints as shown. (A comment on the site describes this method of construction.) I have only basic tools and minimal carpentry skills. I do have a drill and a circular saw. I'm not sure how durable the shrink film is but it seems fairly inexpensive. I already have a lot of 1x1 and 1x2 scrap lumber, screws and other hardware and some basic carpentry tools.

I found a really cool article on DIY "bubble glazing" from someone in Australia. http://mtbest.net/bubble_glazing.html
However, although it looks totally awesome, I doubt that these bubble wrap interior storm windows could survive two cats and a three year old little boy.

Any advice y'all might have would be much appreciated. I need to reduce my heating costs and keep my home warm/non-drafty for my child. Thanks in advance.

BTW, I tried installing foam weather stripping to seal the windows. My little boy uninstalled it almost immediately. I have window blocks that prevent the bottom sash of the window from more than 4" so he can't fall out but that was enough room for him to get his little hand onto the sill and peel off all of the weather stripping from the bottom of the windows.

BTW, I love this group! I check it out almost every day.

CB