---
title: What causes ice dams, and how do I stop them? | House Tite
url: https://housetite.com/insulation-questions/ice-dams/
description: Ice dams come from heat leaking into the attic. Seal the ceiling, add insulation, ventilate under the roof deck. University of Minnesota Extension and Building Science Corporation sources.
updated: 2026-11-06
---

*Home > Insulation questions > Ice dams*

Insulation questions

# What causes ice dams, and how do I stop them?

**Short answer:** Ice dams form when the roof deck is above freezing while it is below freezing outside and there is snow on the roof [1]. The fix is an airtight ceiling first, then more insulation, then ventilation under the roof deck [1].

## Why they happen

Heat from the house warms the roof, the snow melts, and the water refreezes at the cold eaves. University of Minnesota Extension says air leaking from the house into the attic is, in many homes, “the major mode of heat transfer that leads to the formation of ice dams” [2].

## The fix, in order

1. **Seal the ceiling.** “First, make the ceiling air tight so no warm, moist air can flow from the house into the attic space” [2].
2. **Insulate.** Then “consider increasing the ceiling or roof insulation to cut down on heat loss by conduction” [2].
3. **Ventilate.** Keep air moving under the roof deck so any heat that gets there is flushed out [1]. That is why we put baffles at the eaves.

Joe Lstiburek of Building Science Corporation puts it plainly: “airtightness is more important than insulation levels. But both are important” [1].

ENERGY STAR lists a history of ice dams as a sign of serious air leaks [3]. [Attic insulation.](https://housetite.com/attic-insulation/)

## More questions

### Will more insulation stop ice dams?

It helps, but air sealing comes first. Building Science Corporation says airtightness is more important than insulation levels, though both matter.

### Get a price

Call or text a photo of your attic hatch or crawl space. We come out, measure, and give you one written price for the whole job.

Get a price

Call 740-590-5352

### Related

- [Attic insulation](https://housetite.com/attic-insulation/)
- [Do I need more insulation?](https://housetite.com/insulation-questions/do-i-need-more-insulation/)
- [Attic R-value in Ohio](https://housetite.com/insulation-questions/attic-r-value-ohio/)

## Sources

1. Building Science Corporation, Joseph Lstiburek. [BSI-046: Dam Ice Dam](https://buildingscience.com/documents/insights/bsi-046-dam-ice-dam).
2. University of Minnesota Extension. [Dealing with and preventing ice dams](https://extension.umn.edu/garden-and-home/home-maintenance/caring-for-a-home/dealing-with-and-preventing-ice-dams).
3. ENERGY STAR. [A Do-It-Yourself Guide to Sealing and Insulating with ENERGY STAR (2016)](https://www.energystar.gov/sites/default/files/asset/document/DIY_Guide_2016.pdf).

[All insulation questions](https://housetite.com/insulation-questions/)

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**House Tite** · insulation contractor · Nelsonville, Ohio · call or text 740-590-5352 · sprayfoam@housetite.com · Monday to Friday, 8 AM to 5 PM Eastern. Weekends by appointment. Get a price: https://housetite.com/quote/ (or text a photo of the attic or crawl space to 740-590-5352).