You are hearing conflicting opinions because you aren't getting enough information. It depends on the area you are living in, the species of tree, and how well you have cared for that tree over the years.

Some trees are naturally weak, shed branches freely and fall over in a breeze. Some naturally strong-rooted, sturdy tree species can be turned into trees that fall over easily by bad planting, watering and pruning practices.

Unless the house is totally uninsulated walls and attic, shading the windows is all it takes to cut the heat buildup. Some vines on a trellis will do just as well as a 40-foot cottonwood, and be a lot safer.

Also, you need to plant some trees away from you foundation because the roots on some can destroy it. Had a neighbor years ago had basement water problems. The silver maples roots 20 ft away was pushing in the basement walls. I guess they have massive roots. Had to be removed and some work on the basement walls.

Here is a link that might be useful: trees

The answer is, as with so many other things in landscaping, "it depends." Lazygardens has touched on some of the variables.

Trees do have a unique cooling impact because, in my experience, they not only produce shade but also hold a reservoir of cool air underneath them. Hence I would disagree that a vine on a trellis and a tree produce quite the same effect.

But trees do represent a rather unique threat as well. I lived for years under a neighbour's tree that was positioned perfectly to fall on and crush our house. That is a strain I think people have a right to put on themselves, but not to put on other people. So I would always make sure that such a tree is planted so that any threat it creates is to your house, not so that prevailing winds make it a threat to the neighbour's house (ahem).

One problem with making this decision - which I presume is what you are doing - is that you can only make the decision to plant the tree. Most of us will not be granted the opportunity (or the capacity!) to be the person who also has to make decisions about its demise vs. survival 50 or more years hence. And the reality is that, while a tree out in a field or in a forest can grow and grow and grow, in an urban environment, there is such a thing as a tree that is simply too big and has to be taken down.

The best you can do is make a decision that is rational for now and for any conditions you can foresee. You can plant the tree so it will give shade, and so that it will not hit power lines, and so that the majority of its undesirable effects fall on you (debris, roots, canopy, threat) and not the neighours. But you cannot control decisions that future owners of your home make many years from now. If someone is stupid enough to let the tree grow too big and it falls on them, you can't protect them from that.

KarinL

I lived for years under a neighbor's tree that was positioned perfectly to fall on and crush our house. That is a strain I think people have a right to put on themselves, but not to put on other people.

One way to get the problem resolved is to ask YOUR insurance company to contact the other person's insurance company and point out the hazard ... the payer would be the insurance company whose policy covered the property where the tree's trunk was.

We did this for a clump of overgrown pines (too many, too close together, weak roots, huge things) and the insurance companies decided that they would get bids on the removal rather than pay way more when they crashed down onto us. The other homeowner paid his deductible (about $600) and the insurance companies paid the rest.

We let the tree removal guys bring their equipment into our yard, which cut the bill considerably, and it was done as a non-emergency removal.