I am slowly replacing my house's storm windows with very high efficiency weathertight ones with Low-E glass. In the rooms I have completed so far it makes a huge difference...its just about as good as modern windows but you get to keep the nice original to the house wood single pane type.

I guess my gas bill averaging $145-175 this winter is pretty good considering I keep the t-stat for the house at 69F 24/7....my garage is partially heated (to about 55F) and the water entering my normal-type water heater is about 35 degrees this time of year.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)