9 V.S.A. § 4459

(a) If within 30 days of notice, the landlord fails to repair a minor defect in order
 to comply with this chapter or a material provision of the rental agreement, the tenant
 may repair the defect and deduct from the rent the actual and reasonable cost of the
 work, not to exceed one-half of one month’s rent. The tenant shall provide the landlord
 with actual notice of the cost of the repair when the cost is deducted from the rent.