First off, you will NEVER find heat tape at Home Depot, since it is not CSA approved, and from what I understand, is not approved for use in the states either.
Mason - the stuff you're talking about is heat rope, and it has a disc on it that senses temperature, and won't activate the heat until it hits -40. Because this disc has to be removed for it to work, that also means it's not approved for usage, and if it catches fire, well.... kiss your insurance bye bye.
However, many people use heat tape with no probs. The Bean Farm in the states, or Port Credit Pet Centre in Canada is where you'd go to find it. PCPC also has heat rope that IS approved, I believe.